JP2001157469A - Power source system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a stress applied to a circuit constituting component by suppressing the impedance change of a load when increased at an output. SOLUTION: A capacitor Cin is connected as the impedance element of a feedback means in parallel with a diode Di. A capacity value changing circuit 10 having a series circuit of a capacitor C4 having a variable amount and a bipolar transistor Q3 is connected in parallel with the capacitor Cin. If the output is increased by decreasing a load impedance like at a low temperature, the transistor Q3 is turned on, the capacitor C4 is connected in parallel with the capacitor Cin to increase the apparent capacity value of the capacitor Cin, and hence the increase in the output is suppressed. As a result, the increase in the output is suppressed when the output is increased in association with the change of the impedance of the load, and hence the stress applied to the circuit constituting component can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply.

[0002]

2. Description of the Related Art A circuit diagram of a conventional power supply device is shown in FIG. In this circuit, the AC voltage of the AC power supply Vs input through the filter F is full-wave rectified by a rectifier DB such as a diode bridge. Between the DC output terminals of the rectifier DB,
A series circuit of a capacitor C1 for smoothing and a diode D1 is connected via a series circuit of diodes Din and Di, and a capacitor Cin is connected in parallel to the diode Di as an impedance element as feedback means. A capacitor Cf is connected in parallel to a series circuit of the capacitor C1 and the diode D1. Incidentally, the diode D1 is connected to the polarity for discharging the electric charge of the capacitor C1.

[0003] A series circuit of a pair of switching elements Q1 and Q2 which are alternately turned on / off is connected between both ends of the capacitor Cf, and the switching elements Q1 and Q2 constitute an inverter circuit INV. Switching elements Q1, Q2 are connected to the connection point of switching elements Q1, Q2.
A series circuit of the primary winding n11 of the leakage transformer T1 and the capacitor Ca is connected via the primary winding n1 of the drive transformer T2 for driving the drive circuit 2, and one end of the capacitor Ca is connected to the connection point of the diodes Din and Di. Is done.
The secondary winding n12 of the leakage transformer T1 is connected to the power supply terminals of both filament electrodes of a discharge lamp La (load) made of, for example, a fluorescent lamp, and the leakage transformer T1 is connected between the non-power supply terminals of both filament electrodes. Is connected to a capacitor Cr which forms a resonance circuit together with the leakage inductance. The connection point between the capacitor Ca and the leakage transformer T1 is connected via a diode D2 to the connection point between the capacitor C1 and the diode D1.
Here, capacitors C1 and Cf, diodes D1 and D2
The primary winding n11 of the leakage transformer T1 forms a partial smoothing circuit that partially smoothes the output voltage of the rectifier DB and supplies the output voltage to the inverter circuit INV. Note that the diode D2 is connected to the polarity that allows the charging current to flow through the capacitor C1, so that the capacitor Ca and the leakage transformer T
1 is connected to the capacitor C1 and the diode D
It has a function of clamping to the potential of the connection point with the first node.

Further, this circuit comprises switching elements Q1, Q
A self-excited drive circuit 1a for turning on / off alternately 2;
A starter circuit 1b for starting self-excited oscillation of the switching elements Q1 and Q2 when the power is turned on.

The driving circuit 1a comprises a series circuit of a resistor R1 connected between the gate and source of the switching element Q1 and a driving winding n2 of the driving transformer T2, and a resistor R2 connected between the gate and source of the switching element Q2. And a series circuit of a driving winding n3 of the driving transformer T2, and a resistor R1 and a driving winding n for preventing an overvoltage from being applied between the gate and the source of the switching elements Q1 and Q2.
2 is connected in parallel with a series circuit of Zener diodes ZD1 and ZD2 whose cathodes are connected to each other, and a series circuit of a resistor R2 and a drive winding n3 is a Zener diode ZD whose cathodes are connected to each other.
3, ZD4 series circuits are connected in parallel.

The starting circuit 1b is connected between a series connection of a resistor R3, a capacitor C3 and a resistor R4 connected between both ends of the capacitor Cf, and between a connection point of the resistor R3 and the capacitor C3 and the gate of the switching element Q1. A connection point between the capacitor C3 and the resistor R4 is connected to a connection point between the switching elements Q1 and Q2.

Next, the operation of this circuit from power-on to preheating will be briefly described. When the power is turned on, current flows from the rectifier DB to the series circuit of the resistor R3, the capacitor C3, and the resistor R4 via the series circuit of the diodes Din and Di, and the capacitor C3 is charged. When the voltage across the capacitor C3 reaches the trigger voltage of the trigger element TD1, the trigger element TD1 turns on, a gate voltage is applied to the gate of the switching element Q1, and the switching element Q1 turns on. When the switching element Q1 is turned on, a resonance current flows through the primary winding n1 of the driving transformer T2, and there is no gate voltage for maintaining the on state of the switching element Q1 due to the driving winding n2, and the switching element Q1 is turned off. Thereafter, a gate voltage for turning on the switching element Q2 is generated in the driving winding n3 connected to the opposite polarity to the driving winding n2, and the switching element Q2 is turned on. Thereafter, the driving circuit 1a
As a result, the switching elements Q1 and Q2 are alternately turned on / off to perform a self-excited oscillation operation.

When the discharge lamp La is started,
The switching element Q is connected to the drive winding n3 of the drive transformer T2.
When a gate voltage for turning on the switching element 2 is generated, an on-time (that is, on-duty) of the switching element Q2 is determined by a preheating circuit (not shown). Since the switching elements Q1 and Q2 perform self-sustained pulsation, if the ON time of one switching element Q2 is determined, the ON time of the other switching element Q1 is naturally determined.

Thereafter, when the winding voltage of the driving transformer T2 is inverted by the resonance operation of the LC resonance circuit, the driving winding n
2, a gate voltage for turning on the switching element Q1 is generated, and the switching element Q1 is turned on. Further LC
When the winding voltage of the driving transformer T2 is inverted again by the resonance operation of the resonance circuit, a gate voltage for turning on the switching element Q2 is generated in the driving winding n3, and the switching element Q2 is turned on. Thereafter, while repeating the same operation as described above, the switching elements Q1 and Q2 perform self-excited oscillation, and a preheating current flows through the filament of the discharge lamp La.

Here, in the preheating circuit, as the preheating current flows, the on-duty of the switching element Q2 becomes approximately 5
0%, and as the on-duty of the switching element Q2 changes, the oscillation frequency of the switching elements Q1 and Q2 decreases, the lamp voltage gradually increases, and a preheating operation is performed. Eventually discharge lamp L
a starts.

Next, the operation during lighting will be described. When the switching element Q1 is on, the capacitor C
When the voltage across in reaches a voltage difference between the output voltage of the rectifier DB (that is, the voltage across the capacitor C2) and the voltage across the capacitor Cf, the rectifier DB → the switching element Q1 → the primary winding n1 of the drive transformer T2 → the leakage. A current flows through the path of the primary winding n11 of the transformer T1, the capacitor Ca, the diode Din, and the rectifier DB. When the switching element Q1 is turned off, the leakage transformer T
1 primary winding n11 → capacitor Ca → capacitor Ci
n → parasitic diode of switching element Q2 → primary winding n1 of driving transformer T2 → primary winding n11 of leakage transformer T1.
in is charged. When the sum of the charging voltage of the capacitor Cin and the output voltage of the rectifier DB exceeds the voltage across the capacitor Cf, the charges of the capacitors Cin and C2 are charged to the capacitor Cf via the diode Din. And
Then, using the capacitor Ca as a power supply, the capacitor Ca →
When a current flows through the primary winding n11 of the leakage transformer T1, the primary winding n1 of the driving transformer T2, the switching element Q2, the capacitor Cin, and the capacitor Ca, and the capacitor Cin runs out of charge, the diode Di turns on.

When the switching element Q2 is turned off and the switching element Q1 is turned on, the primary winding n11 of the leakage transformer T1 → the primary winding n1 of the driving transformer T2 → the parasitic diode of the switching element Q1 → the capacitor Cf
A regenerative current flows through a path from the diode Di → the capacitor Ca → the primary winding n11 of the leakage transformer T1. Thereafter, the capacitor Cf → the switching element Q1 → the primary winding n1 of the drive transformer T2 → the primary winding n11 of the leakage transformer T1 → capacitor Ca → capacitor Cin →
A current flows through the path of the capacitor Cf, and the capacitor Ci
n is charged. When the sum of the charging voltage of the capacitor Cin and the output voltage of the rectifier DB exceeds the voltage between both ends of the capacitor Cf, the capacitor Cf is charged by the charges of the capacitors Cin and C2, and the rectifier DB → the switching element Q1 → the primary of the driving transformer T2. The input current is drawn through the path of winding n1 → primary winding n11 of leakage transformer T1 → diode Din → rectifier DB. The above operation is repeated according to ON / OFF of the switching elements Q1 and Q2, the capacitor Cin is charged and discharged, and the voltage of the sum of the charging voltage of the capacitor Cin and the output voltage of the rectifier DB is the voltage across the capacitor Cf. If the switching element Q2 is turned on during the period when the output voltage of the rectifier DB is higher than the voltage between both ends of the capacitor C1, the input current is drawn, and the rectifier DB → the capacitor C1 →
Diode D2 → Capacitor Ca → Diode Din →
A charging current flows through the smoothing capacitor C1 through the rectifier DB. The discharging operation of the capacitor C1 is performed during a period when the output voltage of the rectifier DB is lower than the voltage across the capacitor C1, and a discharging current flows through a path of the capacitor C1, the capacitor Cf, the diode D1, and the capacitor C1, and the capacitor Cf is charged. Is done. Then, the voltage between both ends of the capacitor Cf becomes a power source of the inverter circuit INV, and the rectifier D
A voltage obtained by partially smoothing the output voltage of B is supplied to the inverter circuit INV.

As described above, the switching elements Q1, Q2
The capacitor Cin repeats charging / discharging with turning on / off of the power supply, and the input current can flow from the AC power supply Vs at high frequency regardless of the level of the output voltage of the rectifier DB. It is possible to suppress the harmonic distortion of the input current with an inexpensive circuit configuration in which only a small filter F for blocking high frequency is provided therebetween.

[0014]

However, in the above-described conventional example, when the discharge lamp La, which is a load, is to be lit in a low temperature environment, the impedance of the discharge lamp La decreases due to the temperature characteristics of the discharge lamp La. The resonance current flowing through the load circuit will be greater than at room temperature. In the case of the above-described conventional example having the self-excited driving circuit 1a, the load impedance (impedance of the discharge lamp La) decreases and the resonance current increases, so that the current on the secondary side of the driving transformer T2 is increased. Increases, and the oscillation frequency of the inverter circuit INV decreases due to the temperature characteristics of the driving transformer T2, so that the current supplied to the load circuit including the LC resonance circuit further increases. In particular, in a circuit configuration in which a part of the resonance current flowing in the load circuit as the input current as in the above-described conventional example, the resonance current increases due to a decrease in the oscillation frequency of the inverter circuit INV and a decrease in the load impedance. As the current increases, the DC voltage Vdc (the voltage across the capacitor Cf) increases, and the output current (resonant current) further increases. In addition, when the load has a negative resistance such as a discharge lamp, the load impedance is further reduced to cause an increase in the resonance current. Accordingly, the output at the time of low temperature operation is higher than that at the time of normal temperature, and the stress applied to the circuit components increases.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the stress applied to circuit components by suppressing the output when the output increases due to a change in load impedance. It is to provide a power supply device which can be used.

[0016]

According to a first aspect of the present invention, there is provided a rectifier for rectifying an AC power supply.
A smoothing capacitor for smoothing the output of the rectifier, an inverter circuit including at least one switching element and converting a DC output to a high-frequency output, a self-excited drive circuit for driving the switching element, and an output terminal of the inverter circuit. In a power supply device including a load circuit including a resonance circuit and a load inserted between the DC output terminal of the rectifier and feedback means for feeding back a part of the high-frequency output of the inverter circuit to the input side, the impedance of the load is changed. It is characterized by providing another control means for controlling a change in output of the inverter circuit to occur in a desired direction.For example, in the case of a load having a negative resistance such as a discharge lamp, the impedance decreases at a low temperature and the inverter circuit has a low resistance. Because the output increases, the circuit is controlled by controlling the output by other control means when the output increases. It is possible to reduce the stress applied to the formed parts.

According to a second aspect of the present invention, in the first aspect of the present invention, a smoothing capacitor is connected to one of the DC output terminals of the rectifier via a diode, thereby forming a series circuit of two switching elements forming an inverter circuit. Is connected to both ends of a smoothing capacitor, a load circuit is connected between a connection point between the DC output terminal of the rectifier and the diode, and a connection point between the two switching elements, and a feedback comprising an impedance element is provided at both ends of the diode. It is characterized by connecting means, and has the same effect as the first aspect of the invention.

According to a third aspect of the present invention, in the first aspect of the present invention, a series circuit of two switching elements forming an inverter circuit is connected to a DC output terminal of the rectifier via a diode, and a DC output terminal of the rectifier is connected to the DC output terminal of the rectifier. A load circuit including a resonance circuit including a resonance inductor and a capacitor between a connection point with the diode and a connection point between the two switching elements, and a secondary winding included in the drive circuit and a control terminal of each switching element. The primary winding of the drive transformer connected to the DC power supply is connected via a DC blocking capacitor, and a smoothing capacitor is connected to the power supply voltage of the AC power supply via one of the switching elements and a step-down chopper inductor. Auxiliary power supply means for charging to a voltage lower than the peak value is provided, and feedback means comprising an impedance element is connected to both ends of the diode. It features a composed, performing an operation similar to the invention of claim 1.

According to a fourth aspect of the present invention, in the first aspect, a series circuit of two switching elements forming an inverter circuit is connected to a DC output terminal of the rectifier via a diode, and the DC output terminal of the rectifier is connected to the DC output terminal of the rectifier. A primary winding of a transformer having a load connected to a secondary winding between a connection point with the diode and a connection point between the two switching elements, and a load circuit including a resonance circuit including a resonance inductor and a capacitor. The secondary winding included in the drive circuit is connected to the primary winding of the drive transformer connected to the control terminal of each switching element via a DC blocking capacitor, and one of the switching element and the transformer is connected. Auxiliary power supply means for charging the smoothing capacitor to a voltage lower than the peak value of the power supply voltage of the AC power supply through the primary winding is provided. Characterized in that formed by connecting a feedback means composed of impedance elements, performing an operation similar to the invention of claim 1.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the control means varies the amount of feedback in the feedback means. The output of the circuit can be controlled.

According to a sixth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the other control means varies the inductance value of the inductor forming the resonance circuit. Is varied, the resonance frequency of the resonance circuit changes, and the output of the inverter circuit can be controlled.

According to a seventh aspect of the present invention, in any one of the first to fourth aspects of the present invention, the control means varies the capacitance value of the capacitor forming the resonance circuit. Is varied, the resonance frequency of the resonance circuit changes, and the output of the inverter circuit can be controlled.

The invention of claim 8 is the invention of claim 2 or 3 or 4
In the invention, the control means is characterized in that the charge amount of the smoothing capacitor is changed, and if the charge amount of the smoothing capacitor is changed, the input voltage of the inverter circuit changes, and the output of the inverter circuit is changed. Can be controlled.

According to a ninth aspect of the present invention, in the fifth aspect of the present invention, the other control means changes the impedance value of the impedance element as feedback means in a direction in which the output of the inverter circuit is suppressed when the output of the inverter circuit increases. Since the impedance value of the impedance element affects the resonance operation of the resonance circuit, the output of the inverter circuit can be suppressed by changing the impedance value.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the impedance element is a capacitor, and the other control means includes a switching element and a variable capacitor connected in parallel with the capacitor. The output of the inverter circuit is detected based on the voltage between both ends of the capacitor, and the switching element is turned on when the output is increased.If the switching element is turned on, the variable capacitor is connected in parallel to the capacitor. And the output of the inverter circuit can be suppressed.

According to an eleventh aspect of the present invention, in the ninth aspect of the present invention, the impedance element is a capacitor, and the control means includes a switching element and a variable capacitor connected in parallel with the capacitor. The output of the inverter circuit is detected based on the input current, and the switching element is turned on when the output is increased.If the switching element is turned on, a variable capacitor is connected in parallel to the capacitor, and The apparent capacitance value increases, and the output of the inverter circuit can be suppressed.

According to a twelfth aspect of the present invention, in the sixth aspect of the present invention, the resonance inductor comprises a leakage transformer having a load connected to the secondary winding, and the control means is provided on the secondary winding of the leakage transformer. AC switch inserted between the intermediate tap and one end of the secondary winding, wherein the AC switch is turned on when the output of the inverter circuit is increased, and the AC switch which is normally turned off is provided. By turning it on, it is possible to increase the leakage inductance value of the leakage transformer and suppress the output of the inverter circuit.

According to a thirteenth aspect of the present invention, in the seventh aspect of the present invention, the control means includes a variable capacitor connected in series to the resonance capacitor, and an AC switch connected in parallel to the variable capacitor. It is characterized in that the AC switch is turned on when the output of the inverter circuit is increased, and the variable capacitor is connected in parallel to the resonance capacitor by turning on the AC switch that is normally turned off, The apparent capacitance value of the resonance capacitor increases, and the output of the inverter circuit can be suppressed.

According to a fourteenth aspect of the present invention, in the invention of the eighth aspect, the resonance inductor comprises a leakage transformer having a load connected to the secondary winding, and the control means is provided on the secondary winding of the leakage transformer. And a series circuit of a DC switch and a diode inserted between the intermediate tap and one end of a smoothing capacitor, wherein the DC switch is turned off when the output of the inverter circuit increases, and is normally turned on. Turning off the DC switch increases the leakage inductance value of the leakage transformer,
The output of the inverter circuit can be suppressed by reducing the charge amount of the smoothing capacitor.

[0030]

(Embodiment 1) FIG. 1 shows an overall circuit configuration in Embodiment 1 of the present invention. However, since the basic circuit configuration and operation of the present embodiment are the same as those of the conventional example, common configurations and operations are denoted by the same reference numerals, and description thereof will be omitted. Will be described only.

In the conventional example shown in FIG. 12, the capacitor Cin connected in parallel with the diode Di near the zero crossing of the AC power supply Vs is used for the LC resonance circuit including the leakage inductance of the leakage transformer T1 and the capacitor Cr. Influencing the resonance operation, the capacitor C
The greater the capacitance value of in, the smaller its influence.
That is, as the capacitance value of the capacitor Cin increases, the output supplied to the discharge lamp La as a load decreases. On the other hand, when the load impedance decreases as in the case of a low temperature, the output increases in the conventional example. In such a case, the increase in the output can be suppressed by increasing the apparent capacitance value of the capacitor Cin. .

In this embodiment, a capacitance variable circuit 10 for varying the apparent capacitance of the capacitor Cin connected in parallel with the diode Di is provided as another control means, and the load impedance is reduced as in the case of a low temperature. When the output increases, the capacitor Cin
Is characterized in that the apparent capacitance value is increased to thereby suppress an increase in output.

FIG. 2 shows a specific example of the circuit configuration of the variable capacitance circuit 10. The switching element Q3 is composed of a field effect transistor connected in parallel with the capacitor Cin.
And a series circuit of the capacitor C4 and an inverter circuit IN
Voltage dividing resistors R6 and R7 for dividing a DC input voltage Vdc (that is, a voltage across the capacitor Cf) Vdc; a capacitor C5 connected in parallel to the voltage dividing resistor R7;
And a Zener diode ZD5 connected to turn on the switching element Q3 when the voltage across the terminal 5 exceeds the Zener voltage.

Next, the operation of the present embodiment when the output is increased (for example, when the temperature is low) will be described.

As described above, the DC voltage Vdc input to the inverter circuit INV also increases at a low temperature due to a decrease in the load impedance of the discharge lamp La. At this time, in the variable capacitance circuit 10, the capacitor C obtained by dividing the DC voltage Vdc by the voltage dividing resistors R6 and R7.
When the voltage across the terminal 5 exceeds the Zener voltage of the Zener diode ZD5, the Zener diode ZD5 conducts and the switching element Q3 turns on, and the capacitor C4 is connected in parallel to both ends of the capacitor Cin via the switching element Q3. Therefore, the apparent capacitance value of the capacitor Cin increases to the value of the combined capacitance of the capacitor Cin and the capacitor C4. As a result, as described above, the degree of influence on the LC resonance circuit is reduced, and an increase in output can be suppressed. Here, the capacitance value of the capacitor C4 may be set to an appropriate value, but is set to a value sufficiently larger than the capacitance value of the capacitor Cin so that when the switching element Q3 is turned on, the capacitor Cin is substantially short-circuited at high frequencies. You may make it become. Although the field effect transistor is used as the switching element Q3 in the present embodiment, the same effect can be obtained by using a bipolar transistor, IGBT, or the like as long as the element performs a so-called DC switch operation for switching only one-way current. To play.

(Embodiment 2) FIG. 3 shows a circuit configuration of a main part according to Embodiment 2 of the present invention. However, since the basic circuit configuration and operation of the present embodiment are the same as those of the conventional example, common configurations and operations are denoted by the same reference numerals, and description thereof will be omitted. Will be described only.

That is, the capacitance variable circuit 1 of the first embodiment
0 detects the DC input voltage Vdc of the inverter circuit INV and varies the capacitance value of the capacitor Cin, whereas the capacitance value variable circuit 11 of the present embodiment varies the AC power supply Vs
It is characterized in that the input current from is detected.

The capacitance variable circuit 11 in the present embodiment
Is a switching element Q3 composed of a field effect transistor connected in parallel with the capacitor Cin and the capacitor C
4, a secondary winding n21 provided in a normal line filter L2 included in the filter circuit F, and a series circuit of a diode D4, a resistor R8, and a capacitor C6 connected between both ends of the secondary winding n21. And the capacitor C6
And a resistor R9 inserted between the gate and drain of the switching element Q3. The collector of the bipolar transistor Q4 is connected to the gate of the switching element Q3 and the emitter is connected to the emitter of the switching element Q3. Is connected to the source.

Next, an operation when the output is increased (for example, at a low temperature), which is a feature of this embodiment, will be described.

Normally, the bipolar transistor Q4 is turned on by an induced voltage generated in the secondary winding n21 of the normal line filter L2, whereby the gate and source of the switching element Q3 are short-circuited and the switching element Q3 is turned off. Therefore, the apparent capacitance value of the capacitor Cin matches the capacitance value of the capacitor Cin. On the other hand, as described above, the AC power supply Vs
And the input current supplied to the main circuit such as the inverter circuit INV also increases. At this time, in the capacitance value variable circuit 11,
When the normal line filter L2 is magnetically saturated, the bipolar transistor Q4 is turned off, whereby the switching element Q3 is turned on, and the capacitor C4 is connected in parallel to both ends of the capacitor Cin. Therefore, the capacitor Ci
Since the apparent capacitance value of n increases to the value of the combined capacitance of the capacitor Cin and the capacitor C4, as described above, L
The degree of influence on the C resonance circuit is reduced, and an increase in output can be suppressed.

The input current is detected by the variable capacitance circuit 11 of the present embodiment. However, the present invention is not limited to this. For example, the output current may change when the output increases, for example, the lamp voltage or the resonance current. May be detected.

(Embodiment 3) In this embodiment, as shown in FIG. 4, the positions of the capacitor C1 and the diode D1 are exchanged with respect to the embodiment 1, and the polarity of the diode D2 is reversed. The charging current of the capacitor C1 is not the switching element Q2 but the switching element Q2.
1 and the other configuration and operation are the same as in the first embodiment.

Thus, also in the present embodiment, when the output increases at a low temperature or the like, the capacitance C
The apparent capacitance value of in can be increased to the value of the combined capacitance of the capacitor Cin and the capacitor C4, and the influence on the LC resonance circuit can be reduced to suppress an increase in output. It is needless to say that the same effect can be obtained even if the variable capacitance circuit 11 of the second embodiment is employed in the present embodiment.

(Embodiment 4) In this embodiment, as shown in FIG. 5, an inductor L3 is connected in series to the high potential side of a smoothing capacitor C1 with respect to Embodiment 1, and the capacitor C1 and the cathode of a diode D1 are connected. The only difference is that the connection point of the first embodiment is connected to the connection point of the switching elements Q1 and Q2 via the diode D3. Omitted.

The circuit operation of this embodiment will be described below.

First, when the switching element Q1 is turned on,
Rectifier DB → switching element Q1 → drive transformer T2
Primary winding n1 → primary winding n of leakage transformer T1
11 → Capacitor Ca → Diode Din → Rectifier DB
The current flows through the path. The switching element Q1 is off,
When the switching element Q2 is turned on, the energy stored in the leakage transformer T1 causes the primary winding n11 of the leakage transformer T1 → the capacitor Cin → the parasitic diode of the switching element Q2 → the driving transformer T
The regenerative current flows through the path from the primary winding n1 to the primary winding n11 of the leakage transformer T1, and the capacitor Cin is charged. When the sum of the charging voltage of the capacitor Cin and the output voltage of the rectifier DB exceeds the voltage across the capacitor Cf, the charge of the capacitors Cin and C2 is changed to the diode Din.
Through the capacitor Cf.

Then, with the capacitor Ca as a power supply, a current flows through the path of the capacitor Ca → the primary winding n11 of the leakage transformer T1 → the primary winding n1 of the drive transformer T2 → the switching element Q2 → the capacitor Cin → the capacitor Ca. When the electric charge of the diode is exhausted, the diode Di is turned on.

When the switching element Q2 is turned off and the switching element Q1 is turned on, the primary winding n11 of the leakage transformer T1 → the primary winding n1 of the driving transformer T2 → the parasitic diode of the switching element Q1 → the capacitor Cf
A regenerative current flows through a path from the diode Di to the primary winding n11 of the leakage transformer T1. Then capacitor C
f → switching element Q1 → primary winding n1 of drive transformer T2 → primary winding n11 of leakage transformer T1 → capacitor Cin → current flows through the path of capacitor Cf to charge capacitor Cin, and both ends of capacitor Cin and capacitor C2 When the sum of the voltages exceeds the voltage Vdc across the capacitor Cf, the capacitors Cin and C2
And the capacitor Cf is charged, and the rectifier DB → the switching element Q1 → the primary winding n1 of the drive transformer T2 → the primary winding n1 of the leakage transformer T1 again.
Input power flows through a path of 1 → diode Din → rectifier DB. The above operation is repeated.

That is, charging and discharging of the capacitor Cin are repeated by the switching operation of the switching elements Q1 and Q2, and the sum of the charging voltage of the capacitor Cin and the output voltage of the rectifier DB and the voltage Vdc across the capacitor Cf are
AC power supply Vs
Supplies the input current.

On the other hand, when the switching element Q2 is turned on, a charging current flows through the capacitor C1 through the path of the rectifier DB → the inductor L3 → the capacitor C1 → the diode D3 → the switching element Q2 → the rectifier DB.
Is charged with a substantially constant voltage. The charging operation of the capacitor C1 is performed only when the output voltage of the rectifier DB is higher than the voltage across the capacitor C1. When the output of the rectifier DB is discharged from the capacitor C1,
This is performed when the voltage is lower than the voltage between both ends, and the electric charge is discharged from the capacitor C1 to the capacitor Cf via the diode D1, and this acts as the power supply of the inverter circuit INV.

In this embodiment as well, when the output increases at a low temperature or the like, the capacitance C
The apparent capacitance value of in can be increased to the value of the combined capacitance of the capacitor Cin and the capacitor C4, and the influence on the LC resonance circuit can be reduced to suppress an increase in output. It is needless to say that the same effect can be obtained even if the variable capacitance circuit 11 of the second embodiment is employed in the present embodiment.

(Embodiment 5) In this embodiment, as shown in FIG. 6, an inductor L3 is connected in series to the high potential side of a smoothing capacitor C1 with respect to Embodiment 3, and the inductor L3 and the anode of the diode D1 are connected. Is connected to the connection point of the switching elements Q1 and Q2 via the diode D3, and one end of the capacitor Ca and the capacitor C1
The only difference is that the diode D2 to which one end of the third embodiment is connected is omitted, and the same components as those of the third embodiment are denoted by the same reference numerals and description thereof is omitted. Also,
The basic operation of this embodiment is the same as that of the fourth embodiment, and a detailed description is omitted.

Thus, also in the present embodiment, when the output increases at a low temperature or the like, the capacitance C
The apparent capacitance value of in can be increased to the value of the combined capacitance of the capacitor Cin and the capacitor C4, and the influence on the LC resonance circuit can be reduced to suppress an increase in output. It is needless to say that the same effect can be obtained even if the variable capacitance circuit 11 of the second embodiment is employed in the present embodiment.

(Embodiment 6) FIG. 7 shows a circuit configuration of a main part according to Embodiment 6 of the present invention. However, since the basic circuit configuration and operation of the present embodiment are the same as those of the conventional example, common configurations and operations are denoted by the same reference numerals, and description thereof will be omitted. Will be described only.

That is, in the first to fifth embodiments, the increase in the output is suppressed by changing the apparent capacitance value of the capacitor Cin when the output increases, whereas in the present embodiment, the DC of the inverter circuit INV is reduced. Input voltage Vdc
And a capacitance variable circuit 12 for varying the apparent capacitance of the resonance capacitor Cr connected to the non-power supply side of the discharge lamp La.

The capacitance variable circuit 12 in the present embodiment
Is the filament of the discharge lamp La and the capacitor C for resonance.
r and a parallel circuit of a capacitor C6 and an AC switch 12a connected between the AC switch 12a and the DC switch 12a when the DC input voltage Vdc is detected and the input voltage Vdc exceeds a predetermined value.
And a control circuit 12b for turning off. The AC switch 12a switches bidirectional current, and includes a diode bridge DB2 having an AC input terminal connected to both ends of a capacitor C6, and a diode bridge DB2.
And a switching element Q6 composed of a field effect transistor having a source and a drain connected to the DC output terminal of the switching element Q6.

The control circuit 12b includes a voltage dividing resistor R1 for dividing the DC input voltage Vdc of the inverter circuit INV.
0, R11, a capacitor C7 connected in parallel to the voltage dividing resistor R11, a bipolar transistor Q7 having a base connected to one end of the capacitor C7 via a resistor R12,
The DC power supply E supplies a bias voltage to the collector of the bipolar transistor Q7 via the resistor R9, and a resistor R13 inserted between the collector of the bipolar transistor Q7 and the gate of the switching element Q6.

When the DC input voltage Vdc is at the normal level, the resistance values of the voltage dividing resistors R10 and R11 are set so that the bipolar transistor Q7 of the control circuit 12b is turned off. Sometimes, electric charge is supplied from the DC power supply E, the switching element Q6 is turned on, the AC switch 12a is turned on, and both ends of the capacitor C6 are short-circuited by the AC switch 12a. On the other hand, when the DC input voltage Vdc rises due to a decrease in the load impedance of the discharge lamp La at a low temperature, the voltage across the voltage dividing resistor R11 rises in the capacitance value variable circuit 12 to turn on the bipolar transistor Q7. The element Q6 is turned off, the AC switch 12a is turned off, and the capacitor Cr is connected to the capacitor C.
6 are connected in series. Therefore, since the apparent capacitance value of the capacitor Cr decreases to the value of the combined capacitance of the capacitor Cr and the capacitor C6, the resonance frequency of the LC resonance circuit, that is, the oscillation frequency of the inverter circuit INV increases, and the increase in output is suppressed. Can be.

It is needless to say that the same effect can be obtained even when the capacitance variable circuit 12 of this embodiment is combined with the main circuits shown in the third to fifth embodiments. Further, as an AC switch 12a, as shown in FIG.
A circuit in which a series circuit of 8, Q9 and diodes D10, D11 are connected in parallel to each other may be used.

(Embodiment 7) FIG. 9 shows a circuit configuration of a main part according to Embodiment 7 of the present invention. However, since the basic circuit configuration and operation of the present embodiment are the same as those of the conventional example, common configurations and operations are denoted by the same reference numerals, and description thereof will be omitted. Will be described only.

That is, in the sixth embodiment, the DC input voltage Vdc of the inverter circuit INV is detected to change the capacitance value of the resonance capacitor Cr. In the sixth embodiment, the resonance inductance, that is, the leakage inductance is changed. It is characterized in that an inductance value variable circuit 13 for varying the leakage inductance of the transformer T1 is provided as another control means.

The variable inductance value circuit 13 in the present embodiment comprises a secondary winding n12 of the leakage transformer T1.
, An AC switch 13a inserted between the intermediate tap provided at one end of the secondary winding 12 and control for detecting the DC input voltage Vdc and turning off the AC switch 13a when the input voltage Vdc exceeds a predetermined value. A circuit (not shown). However, the same configuration as the sixth embodiment can be used for the AC switch 13a and the control circuit.

When the DC input voltage Vdc is at a normal level, the AC switch 13a is turned on, and the intermediate tap and one end of the leakage transformer T1 are connected to the AC switch 13a.
is shorted by a. On the other hand, at low temperatures, the discharge lamp L
DC input voltage Vd
When c increases, in the inductance value variable circuit 13,
Since the control circuit turns off the AC switch 13a, the leakage inductance of the leakage transformer T1 increases and LC
The resonance frequency of the resonance circuit, that is, the inverter circuit INV
And the increase in output can be suppressed.

It is needless to say that the same effect can be obtained even when the inductance value variable circuit 13 of this embodiment is combined with the main circuits shown in the third to fifth embodiments.

(Eighth Embodiment) FIG. 10 shows a circuit configuration of a main part according to an eighth embodiment of the present invention. However, since the basic circuit configuration and operation of the present embodiment are the same as those of the conventional example, common configurations and operations are denoted by the same reference numerals, and description thereof will be omitted. Will be described only.

In this embodiment, as shown in FIG. 10, the primary winding n11 of the leakage transformer T1 is different from that of the first embodiment.
Is provided with an intermediate tap, and the intermediate tap and the capacitor C1 are provided.
, A series circuit of a diode D7 and a DC switch S1 is inserted between one end of the DC switch S1 and the DC switch S1 at normal times.
1 is turned on, and the DC switch S1 is turned off when the output is increased, so that the charge amount changing means 14 for changing the charge amount of the smoothing capacitor C1 is provided as another control means.

In the conventional example and the main circuit configuration of the first embodiment, the switching element Q2, the leakage transformer T
A buck chopper circuit serving as an auxiliary power supply means is constituted by the primary winding n11, the diode D2 and the smoothing capacitor C1, and when the switching element Q2 is turned on near the peak value of the output voltage of the rectifier DB, the rectifier DB →
Capacitor C1 → diode D2 (diode D7 and DC switch S1 in this embodiment) → primary winding n1 of leakage transformer T1 → primary winding n of drive transformer T2
A chopper current flows through the path of 1 → switching element Q2 → diode Di → diode Din → rectifier DB to charge the capacitor C1.

Therefore, the DC switch S1 is normally turned on by a control circuit (not shown), and the chopper current flows through the path of the diode D7 → the DC switch S1 → the primary winding n1 of the leakage transformer T1. When the switch S1 is turned off and the above-mentioned chopper current flows through the path from the diode D2 to the primary winding n1 of the leakage transformer T1 to increase the inductance value of the primary winding of the leakage transformer T1, the resonance frequency of the LC resonance circuit increases. As a result, the output of the step-down chopper circuit decreases. Therefore, as shown in FIG. 11, when the DC switch S1 is turned off, the valley voltage value of the DC input voltage Vdc decreases as compared with when the DC switch S1 is turned on, so that an increase in output can be suppressed. Here, the control circuit is described in the first embodiment.
May be used.

It is needless to say that the same effect can be obtained by combining the charge amount varying means 14 of the present embodiment with the main circuits shown in the third to fifth embodiments.

[0070]

According to the first aspect of the present invention, a rectifier for rectifying an AC power supply, a smoothing capacitor for smoothing an output of the rectifier, and an inverter circuit including at least one switching element and converting a DC output to a high-frequency output. A self-excited driving circuit for driving the switching element, a load circuit including a resonance circuit and a load inserted between the output terminal of the inverter circuit and the DC output terminal of the rectifier, and a part of the high-frequency output of the inverter circuit. In a power supply device having feedback means for returning to the input side, another control means for controlling a change in the output of the inverter circuit caused by a change in the impedance of the load in a desired direction is provided. In the case of a resistive load, the impedance decreases at low temperatures and the output of the inverter circuit increases, so that when such output increases, other control is required. There is an effect that it is possible to reduce the stress on the circuit components by controlling the direction of suppressing the output by stage.

According to a second aspect of the present invention, in the first aspect of the invention, a smoothing capacitor is connected to one of the DC output terminals of the rectifier via a diode to form a series circuit of two switching elements forming an inverter circuit. Is connected to both ends of a smoothing capacitor, a load circuit is connected between a connection point between the DC output terminal of the rectifier and the diode, and a connection point between the two switching elements, and a feedback comprising an impedance element is provided at both ends of the diode. Because it consists of connecting means,
The same effect as that of the first aspect is obtained.

According to a third aspect of the present invention, in the first aspect of the present invention, a series circuit of two switching elements forming an inverter circuit is connected to the DC output terminal of the rectifier via a diode, and the DC output terminal of the rectifier is connected to the DC output terminal of the rectifier. A load circuit including a resonance circuit including a resonance inductor and a capacitor between a connection point with the diode and a connection point between the two switching elements, and a secondary winding included in the drive circuit and a control terminal of each switching element. The primary winding of the drive transformer connected to the DC power supply is connected via a DC blocking capacitor, and a smoothing capacitor is connected to the power supply voltage of the AC power supply via one of the switching elements and a step-down chopper inductor. Auxiliary power supply means for charging to a voltage lower than the peak value is provided, and feedback means comprising an impedance element is connected to both ends of the diode. Since made, the same effects as the invention of claim 1.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a series circuit of two switching elements forming an inverter circuit is connected to a DC output terminal of the rectifier via a diode, and the DC output terminal of the rectifier is connected to the DC output terminal of the rectifier. A primary winding of a transformer having a load connected to a secondary winding between a connection point with the diode and a connection point between the two switching elements, and a load circuit including a resonance circuit including a resonance inductor and a capacitor. The secondary winding included in the drive circuit is connected to the primary winding of the drive transformer connected to the control terminal of each switching element via a DC blocking capacitor, and one of the switching element and the transformer is connected. Auxiliary power supply means for charging the smoothing capacitor to a voltage lower than the peak value of the power supply voltage of the AC power supply through the primary winding is provided. Since formed by connecting a feedback means composed of impedance element, the same effects as the invention of claim 1.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the other control means varies the amount of feedback in the feedback means. , And the output can be suppressed by controlling the inverter circuit when the load impedance decreases as in the case of a low temperature.

According to a sixth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the control means varies the inductance value of the inductor forming the resonance circuit. If the resonance frequency of the resonance circuit changes, the output of the inverter circuit can be controlled, and the output can be suppressed by controlling the inverter circuit when the load impedance decreases, such as at low temperatures. .

According to a seventh aspect of the present invention, in any one of the first to fourth aspects of the present invention, the other control means varies the capacitance of the capacitor forming the resonance circuit. If the resonance frequency of the resonance circuit changes, the output of the inverter circuit can be controlled, and the output can be suppressed by controlling the inverter circuit when the load impedance decreases, such as at low temperatures. .

The invention of claim 8 is the invention of claim 2 or 3 or 4
According to the invention, the other control means varies the charge amount of the smoothing capacitor. Therefore, if the charge amount of the smoothing capacitor is varied, the input voltage of the inverter circuit changes, and the output of the inverter circuit is controlled. Therefore, there is an effect that the output can be suppressed by controlling the inverter circuit when the load impedance is lowered as in the case of a low temperature.

According to a ninth aspect of the present invention, in the fifth aspect of the invention, the other control means varies the impedance value of the impedance element as feedback means in a direction in which the output of the inverter circuit is suppressed when the output of the inverter circuit increases. Because
Since the impedance value of the impedance element affects the resonance operation of the resonance circuit, there is an effect that the output of the inverter circuit can be suppressed by changing the impedance value.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the impedance element is a capacitor, and the control means comprises a switching element and a variable capacitor connected in parallel with the capacitor, and a smoothing element. An increase in the output of the inverter circuit is detected based on the voltage across the capacitor, and the switching element is turned on when the output increases.If the switching element is turned on, a variable capacitor is connected in parallel to the capacitor, and the appearance of the capacitor is apparent. Has the effect that the output of the inverter circuit can be suppressed.

According to an eleventh aspect of the present invention, in the ninth aspect of the present invention, the impedance element is a capacitor, and the control means includes a switching element and a variable capacitor connected in parallel with the capacitor. It detects the increase in the output of the inverter circuit based on the input current of the inverter circuit, and turns on the switching element when the output increases, so if the switching element is turned on, a variable capacitor is connected in parallel to the capacitor, and the apparent appearance of the capacitor There is an effect that the output of the inverter circuit can be suppressed by increasing the capacitance value.

According to a twelfth aspect of the present invention, in the sixth aspect of the invention, the resonance inductor comprises a leakage transformer having a load connected to the secondary winding, and the additional control means is provided on the secondary winding of the leakage transformer. An AC switch inserted between the intermediate tap and one end of the secondary winding, and the AC switch is turned on when the output of the inverter circuit is increased. This has the effect of increasing the leakage inductance value of the leakage transformer and suppressing the output of the inverter circuit.

According to a thirteenth aspect of the present invention, in the seventh aspect of the invention, the other control means includes a variable capacitor connected in series to the resonance capacitor, and an AC switch connected in parallel to the variable capacitor. Since the AC switch is turned on when the output of the inverter circuit is increased, the variable capacitor is connected in parallel to the resonance capacitor by turning on the AC switch that is normally turned off, and the resonance switch is turned on. This has the effect of increasing the apparent capacitance value of the capacitor and suppressing the output of the inverter circuit.

According to a fourteenth aspect, in the eighth aspect, the resonance inductor comprises a leakage transformer in which a load is connected to the secondary winding, and the additional control means is provided in the secondary winding of the leakage transformer. A DC switch and a series circuit of a diode inserted between the intermediate tap and one end of a smoothing capacitor are provided. The DC switch is turned off when the output of the inverter circuit is increased. Turning off the switch increases the leakage inductance value of the leakage transformer, reduces the amount of charge of the smoothing capacitor, and suppresses the output of the inverter circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment.

FIG. 2 is a main part circuit diagram of the same.

FIG. 3 is a main part circuit diagram of a second embodiment.

FIG. 4 is a circuit diagram of a third embodiment.

FIG. 5 is a circuit diagram of a fourth embodiment.

FIG. 6 is a circuit diagram of a fifth embodiment.

FIG. 7 is a main part circuit diagram of a sixth embodiment.

FIG. 8 is a circuit diagram showing another configuration of the AC switch of the above.

FIG. 9 is a main part circuit diagram of a seventh embodiment.

FIG. 10 is a circuit diagram of an eighth embodiment.

FIGS. 11A and 11B are explanatory diagrams of the operation of the above.

FIG. 12 is a circuit diagram of a conventional example.

[Explanation of symbols]

 1a drive circuit 10 variable capacitance circuit DB rectifier INV inverter circuit Q1, Q2 switching element C1 smoothing capacitor Cin capacitor T1 leakage transformer T2 driving transformer

Continued on the front page F term (reference) 3K072 AA02 BA03 BB03 BB05 BC02 BC03 CA14 CA16 DB03 DD04 EB05 EB06 GA02 GB12 GC02 HA01 HA03 5H007 AA08 AA17 BB03 CA02 CB17 CB25 CC32 DC02 DC05

Claims (14)

[Claims] 1. A rectifier for rectifying an AC power supply, a smoothing capacitor for smoothing an output of the rectifier, an inverter circuit including at least one switching element for converting a DC output to a high-frequency output, and driving the switching element. A self-excited drive circuit, a load circuit including a resonance circuit and a load inserted between an output terminal of the inverter circuit and a DC output terminal of the rectifier, and feedback means for feeding a part of the high-frequency output of the inverter circuit back to the input side The power supply device further comprises means for controlling a change in output of the inverter circuit caused by a change in impedance of the load in a desired direction. 2. A rectifier, wherein a smoothing capacitor is connected to one DC output terminal of the rectifier via a diode, and a series circuit of two switching elements forming an inverter circuit is connected to both ends of the smoothing capacitor. A load circuit is connected between a connection point between the DC output terminal and the diode and a connection point between the two switching elements, and feedback means comprising an impedance element is connected to both ends of the diode. Item 7. The power supply according to Item 1. 3. A series circuit of two switching elements forming an inverter circuit is connected to a DC output terminal of the rectifier via a diode, and a connection point between the DC output terminal of the rectifier and the diode and a connection point of the two switching elements are provided. Between the connection points, a load circuit including a resonance circuit including a resonance inductor and a capacitor, and a primary winding of a drive transformer included in the drive circuit and having a secondary winding connected to a control terminal of each switching element. Auxiliary power supply means connected via a DC blocking capacitor and charging a smoothing capacitor to a voltage lower than the peak value of the AC power supply voltage via one of the switching elements and a step-down chopper inductor. 2. A power supply device according to claim 1, wherein feedback means comprising an impedance element is connected to both ends of the diode. Place. 4. A series circuit of two switching elements constituting an inverter circuit is connected to a DC output terminal of the rectifier via a diode, and a connection point between the DC output terminal of the rectifier and the diode and a connection point of the two switching elements are provided. Between the connection points, a primary winding of a transformer in which a load is connected to a secondary winding, a load circuit including a resonance circuit including a resonance inductor and a capacitor, and a secondary winding included in a drive circuit. The primary winding of the drive transformer connected to the control terminal of the switching element is connected via a DC blocking capacitor, and the smoothing capacitor is connected to the AC winding via one of the switching elements and the primary winding of the transformer. Auxiliary power supply means for charging to a voltage lower than the peak value of the power supply voltage of the power supply is provided, and feedback means comprising an impedance element is connected to both ends of the diode. 2. The method according to claim 1, wherein
The power supply as described. 5. The power supply device according to claim 1, wherein the other control means varies a feedback amount in the feedback means. 6. The power supply device according to claim 1, wherein the control means varies an inductance value of an inductor forming a resonance circuit. 7. The control device according to claim 1, wherein the control means varies a capacitance value of a capacitor forming the resonance circuit.
The power supply device according to any one of claims 1 to 4. 8. The power supply device according to claim 2, wherein the other control means varies a charge amount of the smoothing capacitor. 9. The power supply according to claim 5, wherein the control means varies the impedance value of the impedance element as feedback means in a direction in which the output of the inverter circuit is suppressed when the output of the inverter circuit increases. apparatus. 10. The method according to claim 1, wherein the impedance element is a capacitor, and the control means includes a switching element and a variable capacitor connected in parallel with the capacitor, and the output of the inverter circuit is increased based on the voltage across the smoothing capacitor. 10. The power supply device according to claim 9, wherein a switching element is turned on when the output is increased. 11. The method according to claim 11, wherein the impedance element is a capacitor, and the control means includes a switching element and a variable capacitor connected in parallel with the capacitor, and increases an output of the inverter circuit based on an input current from the AC power supply. The power supply device according to claim 9, wherein the switching device is turned on when the output is detected and the output is increased. 12. The resonance inductor comprises a leakage transformer having a load connected to a secondary winding, and the control means comprises a connection between an intermediate tap provided on the secondary winding of the leakage transformer and one end of the secondary winding. The power supply device according to claim 6, further comprising an AC switch inserted between the AC power supply and the AC switch when the output of the inverter circuit increases. 13. The control device according to claim 1, further comprising a variable capacitor connected in series to the resonance capacitor, and an AC switch connected in parallel to the variable capacitor. 8. The power supply according to claim 7, wherein the power supply is turned on. 14. The resonance inductor comprises a leakage transformer having a load connected to a secondary winding, and the other control means includes an intermediate tap provided on the secondary winding of the leakage transformer and one end of a smoothing capacitor. 9. The power supply device according to claim 8, further comprising a series circuit of a DC switch and a diode inserted therebetween, wherein the DC switch is turned off when the output of the inverter circuit increases.