JP2984012B2 - Switching power supply - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply, and is used, for example, in a discharge lamp lighting device for lighting a discharge lamp at high frequency.

[Prior Art] FIG. 7 shows a schematic configuration of a conventional inverter device. Hereinafter, the circuit configuration will be described. DC power supply E ₁
The inductor L ₁ is connected via a switching element Tr _1. At both ends of the switching element Tr _1, a capacitor C ₁ for smoothing is connected via the diode D ₁ of the reverse-current blocking. Switching element Tr ₁ is switched at a high frequency by a chopper control circuit 5a. When the switching element Tr ₁ is on, a current flows from the DC power supply E ₁ through the inductor L ₁ and the switching element Tr ₁ ,
Electromagnetic energy is accumulated in inductor L _1. Next, when the switching element Tr ₁ is turned off, the electromagnetic energy accumulated in inductor L _1, electromotive force is generated in the direction to keep supplying a current to the inductor L _1, the electromotive force and the voltage of the DC power source E ₁ are added, it is charged in the capacitor C ₁ through the diode D _1. Thus, the capacitor C ₁ high DC voltage can be obtained from the DC power supply E _1. As described above, the step-up type chopper device 1 is configured.

Then, in the inverter apparatus 2 converts the DC power output from the chopper device 1 to a high frequency power, supplied to the load 3 via the inductor L ₃ of current limiting. The configuration of the inverter device 2 is not particularly limited, but includes one or two or more switching elements for switching the input DC power. This switching element
Switching is performed at a high frequency by the inverter control circuit 5b. The current limiting inductors L ₁ and L ₃ in the chopper device 1 and the inverter device 2 are provided with secondary windings L ₂ and L ₄ , respectively. Power obtained in the secondary winding L ₂ is supplied to the inverter control circuit 5b, there is a operating power supply of the same circuit. The power obtained in the secondary winding L ₄ are supplied to the chopper control circuit 5a, which is the operating power supply of the circuit.

[Problems to be Solved by the Invention] However, in the above-described conventional example, when the output power of the chopper device 1 or the output power of the inverter device 2 changes, the power supply from the secondary windings L ₂ and L ₄ changes. There is a problem of doing.

Now, in the conventional example shown in FIG.
, And only the chopper device 1 is examined as shown in FIG. In this device, when giving a lot of energy to the load 3, by increasing the ON period of the switching element Tr _1, it is necessary to increase the current I ₁ flowing through the inductor L _1. Here, the mutual inductance of the inductor L ₁ and its secondary winding L ₂ When M,
Since V _L2 = M (ΔI ₁ / Δt), when the current I ₁ flowing through the inductor L ₁ increases, the voltage obtained in the secondary winding L ₂
V _L2 also increases. Conversely, if less energy given to the load 3, to shorten the ON period of the switching element Tr _1, it is necessary to reduce the current I ₁ flowing through the inductor L _1. In this case, the inductor L ₁ Secondary winding L ₂
The voltage V _L2 obtained at the same time also decreases. Therefore, the electric power supplied to the load 3, the relationship between the voltage V _L2 obtained in the secondary winding L ₂ of the inductor L ₁ is as shown in Figure 9.

Similarly, in the inverter device 2 shown in FIG.
Voltage obtained at the secondary winding L ₄ of the inductor L ₃ of the current limiting is
It fluctuates greatly depending on the power supplied to the load 3. Therefore, the conventional example shown in FIG. 7 has a problem that stable power supply to the chopper control circuit 5a and the inverter control circuit 5b cannot be performed.

The present invention has been made in view of such a point,
An object of the present invention is to provide a switching power supply device including a chopper device and an inverter device that can obtain stable power from the inductor of the chopper device and the inductor of the inverter device regardless of the power supplied to the load. .

[Means for Solving the Problems] In the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, a chopper device 1 for replacing an input power supply with a DC power supply, An inverter device 2 for converting output power into high-frequency power and supplying the high-frequency power to a load 3; the inverter device 2 is a switching power supply device having a resonance circuit in which the resonance current decreases as the power supplied to the load 3 increases. Te, an output of the secondary winding L ₂ of the inductor L ₁ of the switching current of the chopper device 1 flows, the inductor L ₃ of the resonant current of the inverter apparatus 2 flows
It is characterized in further comprising a combining circuit 4 which combines the output of the secondary winding L ₄ for.

Here, a circuit configuration of the inverter device 2 will be described. The series circuit of the switching elements Tr ₂ and Tr ₃ is connected to the DC input terminal of the inverter device 2. One switching element Tr ₃ includes an inductor L ₃ for current limiting and resonance,
Via the capacitor C ₈ for cutting direct current, a parallel circuit of a capacitor C ₉ and the load 3 for resonance is connected. The switching elements Tr ₂ and Tr ₃ are alternately turned on and off at a high frequency by the control circuit 5. When the switching element Tr ₂ is turned on, the inductor L ₃ from the capacitor C _1, the capacitor C ₉ and the load 3, a current flows through the capacitor C _8. When the switching element Tr ₃ is turned on, the power supply capacitor C _8, capacitor C ₉ and the load 3, the inductor L _3, a current flows through the switching element Tr _3. This allows
A high-frequency current flows through the load 3. Inductor L ₃ and capacitor C ₉ constitute a resonance circuit, the resonance voltage generated across the capacitor C ₉ is applied to the load 3. Capacitor C ₈ for DC cut has a larger capacity than the capacitor C ₉ for resonance, it does not contribute to the resonance.

Note that the inverter device 2 is not limited to the circuit configuration shown in the drawing, but may be provided with a resonance circuit in which the resonance current decreases as the power supplied to the load 3 increases.

[Operation] FIG. 2 shows resonance characteristics of the inverter device 2 used in the present invention. In the figure, A is a resonant characteristic curve of the no-load, f _A is the no-load resonance frequency. Also, B is the resonance characteristic curve when there is a load, the resonant frequency when f _B have a load. The operating frequency of the inverter device 2 when there is a load is set as follows.

(I) In an inverter that operates in the slow mode when there is no load and operates in the slow mode even when there is a load, the resonance current at the operating frequency f ₁ (> f _A ) under no load is defined as I ₀ , Assuming that the operating frequency at which the resonance current becomes I _{0 at} a given time is f ₀ (> f _B ), the operating frequency f with a load is set in the range of f ₀ ≦ f ≦ f ₁ .

(Ii) In the inverter that operates in the slow mode when there is no load and operates in the fast mode when there is a load, the resonance current at the operating frequency f ₁ (> f _A ) when there is no load is defined as I ₀ , Assuming that the operating frequency at which the resonance current becomes I _{0 at} a given time is f ₀ ′ (<f _B ), the operating frequency f with a load is set in the range of f ≦ f ₀ ′.

(Iii) In an inverter that operates in the leading phase mode when there is no load and operates in the retarding mode when there is a load, the resonance current at the operating frequency f ₁ ′ (<f _A ) when there is no load is I ₀ , The operating frequency at which the resonance current becomes I ₀ when there is a load is f ₀ (> f _B )
Then, the operating frequency f when there is a load is f ₀ ≦ f ≦
Set to the range of f ₁ ′.

(Iv) In an inverter that operates in the phase advance mode when there is no load and operates in the phase advance mode even when there is a load, the resonance current at the operation frequency f ₁ ′ (<f _A ) under no load is I ₀ , The operating frequency at which the resonance current becomes I ₀ when there is a load is f ₀ ′ (<f _B )
Then, the operating frequency f when there is a load is f ≦ f ₀ ′
Set to the range.

In the inverter device 2 satisfying the above conditions (i) to (iv), the resonance current when there is a load is smaller than the resonance current when there is no load. On the other hand, in the chopper device 1, as described above, the switching current when there is a load is greater than the switching current when there is no load. Therefore, if the switching current of the chopper device 1 and the resonance current of the inverter device 2 are combined, a stable output can be obtained.

Embodiment 1 FIG. 3 is a circuit diagram of a first embodiment of the present invention. Less than,
The circuit configuration will be described. DC power is E _1, and the inductor L ₁ is connected through a power switch SW ₁ and the transistor Q _1, to both ends of the transistor Q ₁ is, smoothing capacitor C through the diode D ₁ of the reverse-current blocking ₁ is connected. Transistor Q ₁ is being switched at a high frequency by the output of the chopper control circuit 5a. First, the transistor Q ₁ is the on state, the DC current from the DC power source E ₁ flows in inductor L ₁ through the transistor Q _1, energy is stored in inductor L _1. Next, the transistor
When Q ₁ is turned off, the inductor L ₁ is the voltage generated at both ends, a voltage obtained by adding the voltage across the inductor L ₁ to the voltage of the DC power source E ₁ is applied to the capacitor C ₁ through the diode D ₁ Is done. Thus, it is possible to obtain a voltage higher than the voltage of the DC power source E ₁ to the capacitor C _1. Thus, the chopper device 1 is configured. Next, the configuration of the inverter device 2 will be described.

A series circuit of transistors Q ₂ and Q ₃ is connected in parallel to both ends of the capacitor C ₁ , and diodes D ₄ and D ₅ are connected in anti-parallel to the transistors Q ₂ and Q ₃ , respectively. At both ends of the transistor Q ₂ is, inductor L _0, L _3, via a capacitor C _3, the discharge lamp Z is connected. Capacitor C ₉ is connected in parallel to the non-power supply side of the discharge lamp Z. Inductor
L ₀ and L ₃ constitute an LC resonance circuit together with the capacitor C ₉ , and the load current becomes an oscillating current. Thus, 2 of the inductor L ₃
The winding L _5, a voltage that varies in polarity according to the oscillation current flowing in the load is induced, the induced voltage transistor Q ₂
It is applied between the base and the emitter of the causes switching transistor Q _2. The base of the transistor Q ₃ are the output signal of the inverter control circuit 5b is supplied. Inverter control circuit 5b detects the voltage across the transistor Q _3, is intended to turn on for a predetermined time transistor Q ₃ from the fall voltage across the transistor Q ₃ is.

The inverter device 2, when the power switch SW ₁ is turned on, and a starting circuit for starting the self-excited oscillation operation. This startup circuit is activated by turning on the power.
C ₂ is charged through the resistor R _2, a diac DA ₁ when the charging voltage reaches the breakover voltage of the diac DA ₁
There turned, first be turned on the transistor Q ₃ by flowing a base current through the diac DA ₁ to the base of the transistor Q _3, it is intended to start the oscillation operation. When the transistor Q ₃ is turned on, the voltage across becomes "Low" level. As a result, the inverter control circuit 5b is triggered, the output thereof becomes “High” level, and the transistor Q
The on state of ₃ is maintained. When Toranjita Q ₃ is turned on, and conducts the diode D _3, since the capacitor C ₂ will not be charged, the starting circuit is stopped. In this case, the secondary winding L ₅ of the inductor L _3, so are wound polarity such as to apply a reverse bias voltage between the base and emitter of the transistor Q _2, the transistor Q ₂ is kept off .
Then, after a predetermined time, the output of the inverter control circuit 5b becomes "Low" level, the transistor Q ₃ are turned off. When the transistor Q ₃ is turned off, the residual inductance of the inductor L _0, L ₃ generates a reverse induced voltage by the collector current of the transistor Q ₃ is reduced, the oscillating current flowing through the inductor L _0, L ₃ in the same direction since attempts to flow, the diode D ₄ becomes conductive. Further, by the secondary winding L ₅ of the inductor L ₃ generates a reverse induced voltage, the transistor Q ₂ is forward biased, the transistor Q ₂ is turned on. When the current of the diode D ₄ becomes zero, current flows through the transistor Q ₂ accumulated charge in the capacitor C ₈ as a power source. At this time, the cores of the inductors L ₀ and L ₃ are linearly magnetized toward the saturation magnetic flux. Eventually, the core reaches saturation flux, inductance rapidly toward the direction of zero, so that the time variation of the collector current of the transistor Q ₂ is infinite. The collector current of the transistor Q ₂ reaches hfe times the base current, the transistor Q ₂ is made an unsaturated state, the transistor Q ₂ base current is fed back by the secondary winding which L ₅ decreases is turned off. Even after the transistor Q ₂ is turned off, the oscillating current flowing through the inductor L _0, L ₃ is about to flow in the same direction, the diode D ₅ is rendered conductive, the inductor L _3, the discharge lamp Z, a capacitor C _8, the inductor L Current flows through the _zero path. When the diode D ₅ is conducting, since the voltage across the transistor Q ₃ are zero, the inverter control circuit 5b is triggered, the output of the inverter control circuit 5b becomes "High" level, the transistor Q ₃ are forward biased . After oscillating current flowing through the diode D ₅ is zero, the inductor L ₀ from the capacitor C _1, the capacitor C _8, the discharge lamp Z, inductor L _3, a current flows through a path of the transistor Q _3. Hereinafter, by repeating the above operation, the oscillation operation of the inverter is continued.

The inverter control circuit 5b is a monostable multivibrator IC composed of a general-purpose integrated circuit (for example, NEC µPD4538).
_{It has two} . This monostable multivibrator IC ₂
The falling trigger input terminal B changes from “High” level to “L”.
ow "level, the output terminal Q goes to" Hig
h ”level and the output terminal goes to“ Low ”level. In this embodiment, the voltage across the transistor Q ₃ is detected by voltage division by a series circuit of resistors R ₃ and R ₄ , and the voltage of the monostable multivibrator IC ₂ is detected. is a trigger signal. capacitor C ₆ is for noise prevention. monostable multivibrator output terminal Q of the IC ₂ is "High" at a level time (the output terminal is "L
ow "time to become level), the resistance R ₁₁ and is determined by the time constant of the capacitor C _7. Output terminal Q driver transistor Q ₇
Is connected to the base, the output terminal is connected to the base of the transistor Q ₈ for driving. The positive electrode of the capacitor C ₁₀ The collector of the transistor Q ₇ is connected through a resistor R _12, the emitter of the transistor Q ₈ is connected to the negative electrode of the capacitor C _10, respectively connected, the emitter of the transistor of the transistor Q ₇
The collector of Q ₈ is connected to the base of the transistor Q _3. Therefore, the monostable multivibrator IC ₂
It operates as a timer circuit for determining the ON period of the transistor Q _3.

Next, the chopper control circuit 5a includes an oscillation circuit IC ₁ consisting integrated circuit for switching regulator control of a general purpose (e.g., Mitsubishi Electric Corporation manufacturing M5T494). The oscillation circuit IC ₁ 'capacitor C ₃ -C ₅ and the resistor R ₈ ~R _10, R ₁₄
Connected to switches alternately output terminal (pin 8) to the open state and the ground state at a period determined by the time constant of the capacitor C ₃ and resistor R _8. The voltage of the capacitor C _10, the resistor R _6, is divided by the series circuit of the R _7, it is applied to the base of the transistor Q _6, the output terminal (8 of the oscillation circuit IC ₁ 'to the base of the transistor Q ₆ No. pin is connected. Thus, the transistor Q ₆ is turned on and off in accordance with the oscillation period of the oscillating circuit IC _1. The collector of the transistor Q ₆ is pulled up through a resistor R _5, the collector potential becomes the square-wave voltage is equal to the oscillation period of the oscillating circuit IC _1. Transistor to Q ₁ chopper device 1 via a totem-pole circuit the voltage consisting transistor Q _4, Q ₅
To supply.

In the present embodiment, the secondary winding L ₂ of the inductor L ₁ in chopper device 1, the secondary winding L ₄ of the inductor L ₃ connected in series in the inverter apparatus 2, both the secondary winding L ₂ , L
The current output from ₄ to charge the capacitor C ₁₀ through the diode D ₆ and resistor R _13, a Zener diode ZD ₁
In to regulate the voltage of the capacitor C _10, to obtain the operating power of the chopper control circuit 5a and an inverter control circuit 5b. It should be noted that, at the time of the input power switch SW _1, the chopper device 1
Since but not operating, the capacitor C ₁₀ through the resistor R ₁
Is to charge. This makes the chopper control circuit
5a and an inverter control circuit 5b starts operating, by the chopper device 1 is operated, is charged capacitor C _1, the voltage rises capacitor C _2, and conducts diac DA _1, the inverter 2 is operated I do. Thereafter, the capacitor C ₁₀ is charged by the secondary winding L _2, electromotive voltage obtained L ₄ of the inductor L _1, L _3.

Thus, in the present embodiment, the chopper device 1
The primary winding L _{2 of the} inductor L ₁ through which the switching current flows
Since it is intended to capacitor C ₁₀ is charged with the combined voltage of the electromotive force obtained, and the electromotive voltage obtained in the secondary winding L ₄ of the inductor L ₃ of the resonant current of the inverter apparatus 2 flows, either one Even if the voltage of the other decreases, the other voltage increases, so that there is no shortage of the operating voltage.

Embodiment 2 FIG. 4 is a circuit diagram of a second embodiment of the present invention. In the present embodiment, a pair of secondary windings L ₂ and L ₆ are provided on an inductor L ₁ through which a switching current flows in a chopper device, and a pair of secondary windings L ₂ and L ₆ are provided on an inductor L ₃ through which a resonance current flows in an inverter device. Lines L ₄ and L ₇ are provided. And
_One secondary winding of inductor L1 in chopper device
The L ₂ and one secondary winding L ₄ of the inductor L ₃ in the inverter device connected in series combines the outputs of both the secondary winding L _2, L _4, preheating one filament of the discharge lamp Z Along with
The other secondary winding of the inductor L ₁ in chopper device
The L ₆ and the other secondary winding L ₇ of the inductor L ₃ in the inverter device connected in series combines the outputs of both the secondary winding L _6, L _7, to preheat the other filament of the discharge lamp Z It is like that.

In this embodiment, since each filament of the discharge lamp Z is preheated by a combined current of the switching current flowing through the chopper device and the resonance current flowing through the inverter device, it is possible to perform preheating with a stable current. is there. In order to compensate for the operating current shortage in the control circuit, an additional resistor R _15.

Third Embodiment FIG. 5 is a circuit diagram of a third embodiment of the present invention. In the present embodiment, connected to the capacitor C ₁₀ of the secondary winding L ₂ of the inductor L ₁ in chopper device via the diode D _2, the secondary winding of the inductor L ₃ in the inverter device
The L ₄ through a diode D ₆ is connected to the capacitor C _10. Of the two secondary winding L _2, the output voltage of L _4, in the case toward the secondary winding L ₂ of the output voltage is high, the diode D ₂ is conducting,
Capacitor C ₁₀ is charged by the output of the secondary winding L _2, diode D ₆ is a cut-off state. Conversely, when the direction of the output voltage of the secondary state L ₄ is high, the diode D ₆ is rendered conductive and the capacitor C ₁₀ is charged by the output of the secondary winding L _4, the diode D ₂ is the cut-off state . Therefore, in the present embodiment, among the two secondary winding L _2, the output voltage of L _4, results in the capacitor C ₁₀ by any higher output voltage is charged, the power supply voltage of the control circuit Can be prevented from decreasing.

Embodiment 4 FIG. 6 is a circuit diagram of a fourth embodiment of the present invention. In the present embodiment, the secondary winding L ₂ of the inductor L ₁ in chopper device, the secondary winding L ₄ of the inductor L ₃ connected in series in an inverter device, both secondary winding L _2, L the current output from ₄ to charge the capacitor C ₁₁ through the diode D ₆ and resistor R _13, to obtain a reference voltage of the comparator CP. The switching element Q ₃ low resistance R ₁₆ is connected in series. When overcurrent flows in the inverter device, the voltage across the low resistance R ₁₆ increases, the voltage capacitor C ₁₁
It exceeds the reference voltage obtained, since the output of the comparator CP becomes "Low" level, the power supply to the transistors Q _7, Q ₈ is stopped, the oscillation of the inverter device is stopped. As a result, in the present embodiment, it is possible to prevent an overcurrent exceeding the reference value from flowing through the inverter device.

[Effects of the Invention] According to the present invention, as described above, in a switching power supply device combining a chopper device and an inverter device, a resonance circuit in which the resonance current decreases as the power supplied to the load increases increases. Since the secondary winding output of the inductor through which the switching current of the chopper device flows and the secondary winding output of the inductor through which the resonance current of the inverter device flows are combined in the device, the inductors in the chopper device and the inverter device are combined. 2
There is an effect that the output obtained from the next winding can be a stable output regardless of the power supplied to the load.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a basic configuration of the present invention, and FIG.
3 is a circuit diagram of the first embodiment of the present invention, FIG. 4 is a circuit diagram of the second embodiment of the present invention, and FIG. 5 is a circuit diagram of the third embodiment of the present invention. FIG. 6 is a circuit diagram of the fourth embodiment of the present invention.
FIG. 7 is a block diagram showing a schematic configuration of a conventional example, FIG. 8 is a circuit diagram of a chopper device used in the embodiment, and FIG. 9 is an operation explanatory diagram of the embodiment. 1 is a chopper device, 2 is an inverter device, 3 is a load,
4 is a synthesis circuit, 5 is a control circuit, L ₁ and L ₃ are inductors, L ₂ ,
L ₄ is a secondary winding.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-32556 (JP, A) JP-A-62-77860 (JP, A) JP-A-63-39471 (JP, A) JP-A-63-39471 86296 (JP, A) JP-A-1-186170 (JP, A) JP-A-1-248971 (JP, A) JP-A-61-44800 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/24-41/29 H02M 7/48

Claims (3)

(57) [Claims] 1. A chopper device for converting an input power source into a DC power source, and an inverter device for converting output power of the chopper device to high-frequency power and supplying the high-frequency power to a load, wherein the inverter device increases the power supplied to the load. What is claimed is: 1. A switching power supply device having a resonance circuit in which a resonance current is reduced, wherein a secondary winding output of an inductor through which a switching current of a chopper device flows and a secondary winding output of an inductor through which a resonance current of an inverter device flows. A switching power supply device comprising a combining circuit for combining. 2. The switching power supply according to claim 1, wherein the combining circuit is a circuit that uses the larger secondary winding output as a combined output. 3. The synthesizing circuit according to claim 1, wherein an output obtained by superimposing both secondary winding outputs is a synthesized output.
A switching power supply as described.