JPH043598Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an inverter device.

[Background technology]

In a circuit that directly rectifies commercial power without using step-down means such as a transformer and supplies it to an inverter, the control circuit aims at high efficiency (its operating voltage is usually lower than that of a circuit that directly rectifies commercial power). ), a DC power source is used, which is the high-frequency output of an inverter that is stepped down and rectified using a transformer or the like. At this time, when the commercial power supply is first turned on, there is no supply from the inverter to the control circuit, so it is necessary to initially supply it from the commercial power supply side via a resistor or the like. This causes the control circuit to drive the main switching element of the inverter, and thereafter the power supply current for the control circuit is supplied from the inverter output. This is the role of the starting circuit, but the current supplied from this starting circuit causes loss in voltage drop elements such as resistors, which poses a problem in producing a highly efficient inverter device.

This point will be explained with reference to the conventional example shown in FIG. In the figure, V _s is a commercial AC power supply, Sw is a power switch, DB ₁ is the first rectifier bridge, C ₁ is a smoothing capacitor, R _s is a starting resistor, C ₂ is a capacitor as an auxiliary power supply, Z is a control circuit, and Q ₂ is a transistor as a switching element for the drive, T ₂
is the drive transformer, Q ₁ is the transistor as the main switching element, T ₁ is the output transformer,
DB ₂ is the second rectifying bridge and L is the load.

a first rectifying bridge DB ₁ and a smoothing capacitor C ₁ ;
rectifies the current of the AC power supply V _s and outputs the transformer T ₁
A first DC power supply circuit _A1 is configured to supply the primary winding _e1 . A second rectifier bridge DB ₂ that receives and rectifies the output from the auxiliary winding e ₃ of the output transformer T ₁ and a capacitor C ₂ constitute a second DC power supply circuit A ₂ as a power source for the drive circuit Dr. The drive circuit Dr consists of a drive transformer _T2 and its switching transistor _Q2 , and its output signal causes the main switching transistor _Q1 to be switched on.
Turn on/off. The control circuit Z sends a pulse signal to the switching transistor _Q2 to turn it on, and this control circuit Z uses the capacitor _C2 of the second DC power supply circuit _A2 as its input power source. Main switching transistor Q ₁
is inserted into the connection line between the first DC power supply circuit A ₁ and the primary winding e ₁ of the output transformer T ₁ .

When the power switch Sw is turned on, the current of the AC power supply _Vs is rectified by the first rectifier bridge _DB1 . Although a DC voltage is generated in the smoothing capacitor _C1 , the main switching transistor _Q1 is not driven and is therefore non-conductive, and the inverter does not operate. On the other hand, the smoothing capacitor _C2 of the auxiliary power supply is charged through the starting resistor _Rs , and its voltage increases.
When the voltage rises sufficiently, the control circuit Z operates, generates a drive signal, operates the drive transistor _Q2 , and operates the main switching transistor _Q1 via the drive transformer _T2 . When the main switching transistor Q ₁ operates, the output transformer T ₁
A high frequency voltage is generated. This output transformer T ₁
is wound with a feedback winding to the auxiliary power supply, the output of which is rectified by the second rectifying bridge DB ₂ and supplied to the capacitor C _2. From then on, this feedback power is mainly used to supply the power supply to the control circuit Z. is supplied.

This is the outline of startup, and the startup resistance R _s
If the starting current supplied through the device is small, starting may not occur in this way. The reason is as follows. If the starting current supplied through the starting resistor R _s is small, the voltage of the auxiliary power supply capacitor C ₂ will rise slowly, so the control circuit Z will operate with insufficient voltage and the drive transistor Q ₂
conducts, but the main switching transistor Q ₁
An insufficient condition arises to cause conduction. When this condition occurs, the capacitor C ₂ is discharged through the primary winding of the drive transformer T ₂ due to the conduction of the drive transistor Q ₂ , and the voltage no longer increases, resulting in startup failure.

In order to avoid this, the starting current must be increased, but this increases the power loss of the starting resistor _Rs , increases the shape of the starting resistor _Rs , and reduces the efficiency of the entire device.

As a countermeasure to this problem, as shown in Figure 2, starting resistance is
A switching contact r is inserted in series with R _s and capacitor C ₂ , and a relay Ry is provided in parallel with capacitor C _2. After startup, relay Ry opens contact r and no current flows through the starting resistor R _s . There is something devised like this. However, it has the disadvantage that it requires electric power to excite the relay Ry and is expensive.

[Purpose of invention]

The purpose of this invention is to provide an efficient inverter device that can be started reliably even with a small starting current, has low power loss due to starting resistance, and is highly efficient.

[Disclosure of invention]

The inverter device of this invention includes an output transformer, a first DC power supply circuit that rectifies the current of an AC power supply and supplies it to the primary winding of the output transformer, and an inverter that is inserted between the primary winding and the first DC power supply circuit. a main switching element, a drive circuit for the main switching element, a switching element for the drive circuit, a control circuit for transmitting a pulse signal for conduction to the switching element for the drive circuit, and a power switch for the AC power supply. A second DC power supply circuit that starts charging with a minute current when turned on, and is charged by a rectified current of the output of the output transformer in a steady state after startup, and becomes a power source for the drive circuit. The control circuit further includes a third DC power supply circuit that supplies an operating current to the control circuit, and controls the control circuit so that after inputting the operating current, the output of the second DC power supply circuit operates the drive circuit. The device is constructed with a delay circuit so as to transmit a conduction pulse signal to the switching element of the drive circuit after the time period for the switching element to rise to a required level has elapsed.

A first embodiment of this invention will be described based on FIGS. 3 and 4. Control circuit Z is an oscillator
It consists of the OSC, the comparator CO, its peripheral circuits (resistors R ₄ , R ₅ , R ₆ , capacitor C ₄ ), and the AND circuit AND, and its power consumption is extremely small compared to the drive power. ing. A ₃ is a constant voltage Zener diode with resistor R ₃
This is a third DC power supply circuit consisting of _Dz and supplies operating current to the control circuit Z.
The starting resistor R _s is configured to allow a minute current to flow during starting. Since the other configurations are the same as those of the conventional example, the same parts are given the same reference numerals and the explanation will be omitted.

FIG. 4 is a diagram of voltage waveforms at various parts after the power switch Sw is turned on. V _c1 is the voltage of smoothing capacitor C ₁ ,
V _z is the voltage of Zener diode D _z , V _c2 is the voltage of capacitor C ₂ , B is the output voltage of comparator CO,
C is the output voltage (drive voltage) of the AND circuit AND
It is.

The operation will be explained below.

○ When the power switch Sw is turned on, the voltage V _c1 of the smoothing capacitor C ₁ in the first DC power supply circuit A ₁ rises immediately.

The voltage V _z of the Zener diode D _z in the third DC power supply circuit A ₃ also rises following the voltage V _c1 and exhibits a constant voltage, causing the control circuit Z to operate.

○ In the control circuit Z, the resistor R ₄ and the capacitor C ₄ constitute an integrating circuit, and the comparator CO creates a delayed waveform of the voltage V _z . That is,
Immediately after the switch Sw is turned on, the voltage of the capacitor _C4 is small, and the output voltage B of the comparator CO is at a low level. The voltage of the capacitor C ₄ gradually increases, and after a certain period of time according to the time constant of R ₄ ×C ₄ , the output voltage B of the comparator CO is inverted to a high level.

○ The oscillator OSC starts oscillating as soon as the voltage _Vz rises, but while the output of the comparator CO is at a low level, the output voltage C of the AND circuit AND is at a low level, and during this time the drive transistor _Q2 is non-conducting. It is becoming.

○ During this time, the smoothing capacitor C ₂ of the second DC power supply circuit A ₂ is being charged with a minute current via the starting resistor R _s , and its voltage V _c2 is gradually increasing, so that the previous comparator output voltage B is It is sufficiently large at the time when it reverses and reaches a high level.

○ When the comparator output voltage B is inverted to high level, a drive signal appears on the output voltage C of the AND circuit AND, and the drive transistor Q ₂
conducts.

○ When the drive transistor Q ₂ becomes conductive, a voltage approximately equal to the voltage V _c2 appears in the primary winding of the drive transformer T ₂ , and the drive transformer T ₂
A voltage is generated in the secondary winding according to the winding ratio.

○ Since the voltage developed in the secondary winding of the drive transformer T ₂ is large enough to make the main switching transistor Q ₁ conductive, this transistor Q ₁ conducts and the output transformer T ₁ receives the first A pulse is generated.

○ The pulses generated in the auxiliary winding e ₃ in the output transformer T ₁ are rectified by the second rectifying bridge DB ₂ and charge the smoothing capacitor C ₂ .

○ From now on, the power of the second DC power supply circuit A ₂ , that is, the drive power, is mainly obtained from the auxiliary winding e ₃ of the output transformer T ₁ rectified by the second rectifier bridge DB ₂ , and the inverter operates normally. I do.

A second embodiment will be explained based on FIG. Third
The DC power supply circuit _A3 is composed of a resistor _R3 , a capacitor _C3 , and a diode _D3 . The control circuit Z consists of an oscillator OSC and a capacitor _C3 . After turning on the power switch Sw, the delay time until the output of the control circuit Z becomes high level, that is, the waiting time until the capacitor C ₂ is charged by the minute current passing through the starting resistor R _s and reaches a sufficiently large voltage. , is secured by the charging time of capacitor _C3 . The rest is the same as the first embodiment.

The third embodiment will be explained based on FIG. 6. As a peripheral circuit of the comparator CO in the control circuit Z, a resistor _R7 is inserted in place of the capacitor _C4 of the first embodiment, and the resistor _R4 is replaced with a starting resistor. By connecting the capacitor C ₂ to the connection point between R _s and the capacitor C 2, the capacitor C ₂ is substituted for the capacitor C ₄ . The rest is the same as the first embodiment.

[Effect of idea]

According to the inverter device of this invention, it is possible to start up reliably even with a small starting current, and therefore power loss due to starting resistance can be reduced.
This has the effect of realizing efficient operation.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram of a conventional example, Fig. 2 is an electric circuit diagram of another conventional example, Fig. 3 is an electric circuit diagram of the first embodiment of this invention, and Fig. 4 is a voltage diagram of each part. The waveform diagram, FIG. 5, and FIG. 6 are electrical circuit diagrams of the second and third embodiments, respectively. _A1 ...First DC power supply circuit, _A2 ...Second DC power supply circuit, _A3 ...Third DC power supply circuit, _Vs ...AC power supply, Z...Control circuit, Dr...Drive circuit,
Q ₂ ... Drive transistor (drive switching element), T ₁ ... Output transformer, Q ₁ ... Main switching transistor (main switching element).

Claims (1)

[Scope of utility model registration request] an output transformer, a first DC power supply circuit that rectifies the current of the AC power supply and supplies it to the primary winding of the output transformer, a main switching element inserted between the primary winding and the first DC power supply circuit; a drive circuit for the main switching element; a switching element for the drive circuit; a control circuit for transmitting a pulse signal for conduction to the switching element for the drive circuit after a predetermined period of time has elapsed after inputting the operating current; a second DC power supply circuit that starts charging with a minute current when the power switch of the power source is turned on, and is charged by the rectified current of the output of the output transformer in a steady state after startup, and becomes a power source for the drive circuit; a third DC power supply circuit that supplies the operating current to the control circuit, and wherein the predetermined time is set to a time during which the output of the second DC power supply circuit rises to a level necessary for operating the drive circuit. Device.