JPS63136964A - Inverter device - Google Patents

Abstract

PURPOSE:To compensate the output fluctuation of an inverter circuit, by feeding the detection output such as load current, output voltage, etc., back to a control circuit. CONSTITUTION:A half-bridge type inverter circuit B is composed of a DC power source E, diodes D1-D2, capacitors, C1-C2, transistors (hereinafter referred to as Tr) Q1-Q2 for main switching elements, etc., to which a load R is connected as a series resonant circuit. This circuit B is, in addition, started with a starting circuit ST when the power supply is put to work. The load current ILA is detected by a current transformer T2, and rectified and smoothed, etc., by a diode D4, etc., to output to a control circuit S, so that the output voltage fluctuation of the abovementioned inverter circuit B is compensated. The control circuit S is composed of monostable multivibrators IC1-IC2, Tr's Q3-Q4, a comparator IC3, etc. If, then, the ON-OFF ratio of the abovementioned pair of Tr's Q1-Q2 is made variable, then the load fluctuation compensation can be implemented without changing the oscillatory frequency of the inverter circuit B.

Description

[Detailed description of the invention] [Technical field 1 The present invention relates to an inverter device.

[Background technique! ] Figure 9 shows the configuration of an inverter device using a conventional self-excited inverter circuit B, in which transistors Q, , Q, are connected in series with a DC current "m" (including the rectified voltage of the AC power source) E. diodes D1 and D2 are connected in parallel with the transistors Q3 and Q2 with the polarities shown in the figure.The primary 811in of the resonant circuit A including the capacitor C1 and the load R, and the drive transformer T is connected in parallel with the transistor Q. 1 series circuit is connected.The drive transformer T, having a primary winding n, has secondary windings n6, n3, and a secondary winding n2.
is connected to the control resistor R1 of the transistor Q1, and the secondary winding n is connected to the control resistor R2 of the transistor Q2. Resonant circuit A has an inductance and a capacitor C8
, and a load R such as a discharge lamp. Furthermore, the inverter circuit 'B is provided with a starting circuit ST, which consists of a resistor R1 and a capacitor C1 connected in series, and a connection point between the resistor R1 and the capacitor C1. is connected to one end of a bidirectional switching element, such as a diac Q3, the other end of which is connected to the base of the transnoster Q2. Also, the connection point of resistor R31 and capacitor C3 is connected to the nanonode of diode D, and the cathode is connected to the transistor Q.
Connected to the second collector.

The operation of the inverter circuit B described above is as follows. That is, when the power switch SW is turned on, the capacitor C8 is charged via the resistor R1. Then, when the voltage on capacitor C1 reaches the breakover voltage of diac Q, capacitor C1 discharges through the base-emitter junction of transistor Q2. This discharge causes transistor Q2 to
becomes conductive for the first time. Therefore, DC power supply E → capacitor C1
→ Resonant circuit A → One large turn Rn of drive transformer T1 + → Transistor Q2 → Current flows through DC power supply E to charge capacitor C1. Since this current flows through the primary winding n of the drive transformer T1, the two secondary windings mn2 and n3
A voltage is induced in The induced voltage in the secondary winding Mn3 has a polarity (forward voltage) that maintains the conduction state of the transistor Q2. After that, the current increases in an attempt to charge the capacitor C8, but as the charging progresses, the current gradually decreases, and when it approaches zero, the feedback voltage from the drive transformer T1 becomes a forward voltage at the transistor Q1 and a reverse voltage at the transistor Q2. Therefore, transistor Q2 is turned off and transistor Q1 is turned on. Then, a closed circuit is formed between the resonant circuit A, the primary winding n1 of the drive transformer T1, and the transistor Q1, and the capacitor C1 starts discharging.

Due to the vibration caused by this capacitor discharge, the transistor Q1
By repeating charging and discharging of capacitor C1, turning off transistor Q2 and turning on transistor Q2, both transistors Q, Q, are turned on and off alternately, allowing current to flow through resonant circuit A, and resonant voltage generated in capacitor C2. As a result, the discharge lamp, which is the load R, starts and lights up.

However, in such a configuration, transistors Q1 and Q
hFE (DC current amplification factor) of 2, μ of drive transformer T1
Due to variations in S (relative magnetic permeability), tan δ (loss coefficient), the inductance value of the inductance L in the resonant circuit A, the capacitance value of the capacitor C2, etc., the current flowing through the load R, which is a discharge lamp, fluctuates significantly. When the current decreases, a specified illuminance cannot be obtained, and when the current increases, a current exceeding the specified value flows through the load R, which is a discharge lamp, and this adversely affects the life of the discharge lamp.

Also, a large current flows through the transistor Q1%Q2S inductance L, increasing the amount of heat generated. The above-mentioned problems also occur when the voltage of the DC power supply E fluctuates.

As a discharge lamp lighting method that compensates for load fluctuations,
A frequency control method as shown in the f510 diagram is often used. Figure 11 shows a concrete example of the circuit, in which a DC power supply E including a rectified AC power supply is input, capacitors C4 and C5, diodes D1 and D2, and a transistor Q.
1, Q2 constitutes a bar 7 Putulino type inverter circuit B, and the load R is a chitaak foil L1 and a discharge lamp L.
A are connected in series, and a capacitor C6 is connected in parallel to the discharge lamp LA to form a series resonant circuit.

The transistors Q1 and Q2 are controlled by a control circuit S, and a load current detection circuit F detects the lamp current and feeds it back to the control circuit S.

In this configuration, when all the lights are on, transistors Q, Q2 are turned on and off at a certain switching frequency higher than the resonant frequency, as shown in Figure 12(,), and when the load current is large, as shown in Figure 12(b). As shown in FIG. 2, by increasing the setting of the switching frequency of the transistor Q2, the impedance of the resonant circuit can be increased and the lamp current can be reduced.

However, in the above-mentioned system, since the frequency is made variable, there are problems such as an increase in power supply feedback noise and an increase in transistor switching loss when the frequency is increased.

[Objective of the Invention 1 The present invention has been made in view of the above-mentioned problems, and its purpose is to reduce the fluctuation of load current without significantly changing the frequency or increasing the loss of the switching transistor. An object of the present invention is to provide an inverter device with a simple circuit configuration capable of performing compensation.

[Disclosure of the Invention] The present invention provides a DC power supply, an inverter circuit that includes at least one pair of switching elements that alternately turn on and off at a predetermined period, and converts the voltage of the DC power supply into an AC voltage and outputs the AC voltage, and an output of the inverter circuit. The inverter circuit includes a control circuit that changes a ratio of on-periods of the pair of switching elements within the predetermined frequency, and a capacitor connected in series with the load. In the inverter device, the load current,
The present invention is characterized in that fluctuations in the output of the inverter circuit are compensated for by feeding back a detection output such as an output voltage to the control circuit.

The present invention will be explained below with reference to Examples.

'11 Taste A discharge lamp lighting device using an inverter device of the present invention is a self-excited oscillation inverter circuit whose power source is a DC power supply and whose load is a series resonant circuit consisting of an inductance, a capacitor, and a discharge lamp. A sub-switching element is connected in parallel to one feedback input terminal of the switching element, and a part of the output of the inverter circuit is fed back to the control terminal of the sub-switching element via a switch means, and self-oscillation is performed. This device is characterized in that the on/off ratio of the pair of switching elements is made variable by forcibly shortening the on-feedback of one of the pair of switching elements with 11 switching elements.

FIG. 1 shows an embodiment using a bar 7 pulley type inverter circuit. In the same figure, inverter circuit B
uses a DC power supply E as a power source, and is composed of diodes D2, D2, capacitors C1, C2, and transistors Q3, Q2 as main switching elements, etc., and one discharge lamp LA is connected in series on an inductance as a load R. Capacitor C2 is connected in parallel to electric lamp LA,
A series resonant circuit is configured. The starting circuit ST is configured similarly to the starting circuit ST of the circuit shown in FIG. 9, and is for starting the inverter circuit B when the power is turned on.

Furthermore, a transistor Q3, which is a sub-switching element, is connected between the base and emitter of the transistor Q2 via a resistor R2. A control transistor Q4 is connected to the base of the transistor Q, and is turned on and off by the output of the monostable multipipe leak IC2. Furthermore, the monostable multinoy plate IC, IC2 are commercially available ICs.
, MC145388%5N74123N, etc.

Furthermore, the base of transistor Q, and the transistor Q,
The flip-flop connects the resistor RIM to the output of the comparator IC1.
connected via. Comparator ■C3 is composed of an operational amplifier (for example, UPC451), and comparator ■C3 is a detection signal obtained by rectifying and smoothing the secondary output proportional to load current ILA detected by current transformer T2 with diode D1 and capacitor C6. Output voltage vY is compared with reference voltage e. This reference voltage e is obtained by a Zener diode or the like.

And electricity! ) Lance T2% Comparator ■C3, transistor Q 51 Q 4 , monostable multivibrator IC, , IC, etc. to vtJ& the control circuit S that compensates for fluctuations in the output of the inverter circuit B.

Next, the operation of this embodiment will be explained using a waveform diagram of PjS2. First, the monostable multi-IC, IC2 operates as follows. In other words, the input terminal B of the monostable multivibrator IC has the VCIE of the transistor Q2 connected to the resistor R.
4. Voltage obtained by dividing voltage by R5 ■6. (Figure 2 (
b)) is input. monostable multivibrator IC,
A signal Q+, which becomes high level at the fall of the voltage R9, is output from the output terminal Q. This time is determined by the capacitor Ct and the resistor R6 (see FIG. 2(c)). The output signal q of the monostable multivibrator ■C1 is further input to the input ntB2 of the monostable multivibrator IC2, and the output yaks2 of the monostable multivibrator IC2 has a signal that becomes low level at the falling edge of the signal Q+. q2 is output. The low level period of the signal q2 is determined by the capacitor C8 and the resistor R2 (see figure m2 (d)).

This signal q2 is applied to a transistor Q via a resistor R6.

is input to the base of Q, turning transistor Q on and off. Next, the current transformer T2 detects the load current,
This detected output voltage (2) is compared with a reference voltage (e) by a humpator (2) C1. A signal q is outputted to the output terminal of the comparator IC1, as shown in FIG. 3(a), which becomes high level when Vg>e and becomes low level when VK<e. When the load current IL^ increases and becomes Vy>e, the signal q becomes high level. Furthermore, when the signal q2 in FIG. 2(d) is at a low level, the transistor Q is turned off.
Since transistor Q is turned on, transistor Q2 is rapidly turned off. As a result, the on-period of transistor Q2 becomes shorter than the on-period of transistor Q1, and the on-periods of both switching transistors Q, Q2 become unbalanced, and the load current ILA becomes small. This principle has already been proposed by the present inventors in Japanese Patent Application No. 113716/1982.

To summarize the principle, an asymmetric AC waveform is formed in which the positive side waveform and the negative side waveform are not the same (different on duty) by making the on periods of both transistors Q,, Q2 different, and this AC waveform is transferred to the capacitor C1. When applied to the load R via the capacitor C2, the DC component is cut off by the capacitor C2, and power is supplied to the load R according to the asymmetry. Therefore transistor Q
By gradually changing the ON period of Q2 and changing the asymmetry of the AC power supply, the power supplied to the load R can be adjusted. Now, load current 1. When ^ becomes smaller and Vy<e, the output of comparator IC becomes low level, transistor Q is turned off, the on periods of transistors Q, and Q2 become equal, and load current IL^ increases. .

By repeating the above operations, the load current ■.

The output waveform becomes as shown in FIG. 3 (c), and its effective value becomes almost constant, and its fluctuation can be compensated for. Similarly, the same effect can be obtained when the on period of transistor Q is made shorter than the on period of transistor Q2. In addition, the m2 diagram (b) shows the current I flowing through the transistor Q2.
O2% again! Figure 13 (b) shows the signal q2.

In this embodiment, this is achieved by a circuit configuration as shown in the frame of the inverter circuit Blem4.

In other words, the transistor Q7 is connected to the DC power supply E. Q, and transistors Q, , Q, are connected in series, and the transistors Q6. An inductance L is connected to the series circuit of Q and each connection terminal of the transistors Q, , Q@ through a capacitor C1.
, a load R consisting of a series circuit of discharge lamps LA is connected. The control circuit S includes a transistor Q5. Q, and transistors Q, ,Q, are turned on and off alternately.The load current control section C feeds back the load current ILA through the current transformer T2 and instructs the control circuit S to vary the load current. It is a circuit. Therefore, transistors Q, ,Q, and transistors Q,,Q, have DC current yi
An inverter circuit B is configured to convert the DC voltage of E into an AC voltage.

FIG. 5 shows a specific circuit of the control circuit S and load current control section C in FIG.
For example, the circuits IC, IC2 are N made by jrrNTER8IL.
It is composed of E/5E555 or μpcisssc manufactured by NEC Corporation. Resistance R9t R+. , capacitor C5, and timer IC circuit IC1 constitute an astable multivibrator. The output of this timer circuit IC is connected to the trigger terminal of the timer IC circuit IC1. Timer IC circuit IC1, variable resistor R11,
Capacitors C2° and C81 constitute an astable multivibrator. The output of the timer IC circuit C5 is sent to the base of the transistor Q via the resistors R and □, and after being inverted by the inverter IC, the output is sent to the transistor Q via the resistor R17. The base conversion is connected. Transistor Q,,Q,. is turned on and off alternately, and the transformer T
The isolated signal is connected to the resistor R13 to the resistor Ra through the resistor R13 and the resistor Ra
It is supplied between the bases and emitters of transistors Q, , Q, , and Q through respective terminals. FIG. 6 shows signals of various parts of the circuit of FIG.

. Output signal a1 of the timer IC circuit ICs. Figure 6 (
As shown in a), it is a signal with a period t0 determined by the resistor RItRIO and the capacitor C3. This signal a is for timer I
When a voltage of 1/3 Vcc or more (pulse) is applied to the terminal (2) of the C circuit IC9, the output signal shown in FIG. 6(b) becomes "H". This "H" period T1 is determined by the variable resistor RI 1 and the capacitor C++. The voltage C obtained by inverting the signal S in FIG. 6(b) remains "L" during this period T, as shown in FIG. 6(c), for a certain period t.

When the time period elapses, the signal S becomes "L" and the signal C becomes "H".

Therefore, transistor Q, is turned on during period t, and transistor Q,. is turned on during period t2. transistor Q
5(Q,,) turns on and off, transistors Qs, Q, (Q,,Q,) turn on through period t+(tz),
Turn off. Furthermore, the periods T, , T2 can be varied by varying the voltage of the variable resistor R1+ of the control circuit S. As shown in FIGS. 7 and 8, the circuit shown in #S5 achieves control in which the period is made constant and the period is varied.

In other words, when the load current ILA increases, the current transformer T2
Since the detected output voltage vk increases, the capacitor C11 is charged faster by the resistor R11, so the output period L1 of the timer IC circuit ICS becomes shorter than t2, and the on-periods of the transistors Q, Q, and Q7yQ6 become shorter than t2. As shown in FIGS. 7(a) and 7(b), an imbalance occurs and the load current ■LA decreases. When the load current IL^ decreases, the detected output voltage vK by the current transformer T1 decreases, so the charging of the capacitor CI+ becomes slower.
1. As the period of t1 becomes longer and approximately t1=h, the on-periods of transistors Q, , Q and transistors Q, , Q become approximately equal as shown in FIGS. 8(a) and (b), and the load current ILA increases.

By repeating the above operation, the load current ■L
It is possible to keep ^ almost constant.

Incidentally, it is also possible to equivalently compensate for fluctuations in the output of the inverter circuit B by detecting fluctuations in the power supply voltage instead of detecting fluctuations in the load current IL^.

Effects of the Invention J The present invention comprises a DC power supply, an inverter circuit that includes at least a pair of switching elements that alternately turn on and off at a predetermined period, and converts the voltage of the DC power supply into an AC voltage and outputs the AC voltage, and an output of the inverter circuit. The inverter circuit includes a control circuit that changes the ratio of on-periods of the pair of switching elements within the predetermined period, and a capacitor connected in series with the load. In the inverter device, the load current,
By feeding back the detected output such as the output voltage to the control circuit described above, fluctuations in the output of the inverter circuit are compensated for, so load fluctuations can be compensated for without changing the oscillation frequency of the inverter circuit, and as a result, noise can be prevented and switching elements can be This is effective in reducing switch gloss.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of the first embodiment of the present invention, Figs. 2 and 13 are waveform diagrams for explaining the operation of the same as above, Fig. 4 is a circuit diagram of the second embodiment of the present invention, and Fig. 5 is the same as the above. A circuit diagram of the main part, FIGS. 6 to 8 are waveform diagrams for explaining the operation of the same as above, FIG. 9 is a circuit diagram of a conventional example, FIG. 10 is a circuit configuration diagram of another conventional example, and FIG. 11 is the same as above. The circuit diagram of FIG. 12 is a waveform diagram for explaining the operation of the same. R: Load, E: DC power supply, B: Inverter circuit, Q, , Q2: Transistor, S: Control circuit. Agent Patent Attorney Mr. Ishi 1) 7 Figure 7 (b) Qy, Q6 Off On Figure 10 Figure 11 Figure 12 (a) (b)

Claims (1)

[Claims] (1) A DC power source, an inverter circuit that includes at least one pair of switching elements that alternately turn on and off at a predetermined period, and converts the voltage of the DC power source into an AC voltage and outputs it, and is energized by the output of the inverter circuit. In the inverter device, the inverter circuit comprises a control circuit that changes the ratio of on-periods of the pair of switching elements within the predetermined period, and a capacitor connected in series with the load. An inverter device that compensates for fluctuations in the output of an inverter circuit by feeding back detection outputs such as current and output voltage to the control circuit.