JPH0767356A - Power supply device - Google Patents

Abstract

PURPOSE:To obtain a power supply device, in which an on-duty is set in 1:1 and the generation of noises is inhibited, by controlling the magnetic energy of a positive feedback winding by a magnetic-energy control means and controlling another positive feedback winding by magnetic coupling. CONSTITUTION:In a magnetic-energy control means 16, voltage in the direction driving each field-effect transistor Q11, Q12 is rectified by a voltage doubler rectifying circuit 17 and charged to a capacitor C17, and consumed and controlled by an output control circuit 18. Consequently, the quantity of magnetic energy is also reduced, the oscillation frequency of each field-effect transistor Q11, Q12 is lowered and an output from an inverter circuit 11 is increased at the time of the large power consumption of the output control circuit 18 and the oscillation frequency of each field-effect transistor is augmented and an output from the inverter circuit is diminished at the time of small power consumption in the bi-directional magnetic energy of a current transformer CT. Accordingly, the duty ratio of the field-effect transistors reach approximately 1:1, and resonance currents are also brought close to a sine wave and noised 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 device for alternately operating a pair of switching elements.

[0002]

2. Description of the Related Art Conventionally, there are a self-excited type and a separately excited type as a discharge lamp lighting device having a power supply device using an inverter circuit, and the circuit is selectively used according to the purpose. In general, the self-excited type is used for a single-function discharge lamp lighting device that lights a discharge lamp with a constant reference illuminance, and the separately excited type is used for a discharge lamp lighting device having a dimming function. That is, although the self-excited type is inexpensive, it is difficult to arbitrarily control the switching element, and the separately excited type is easy and expensive to arbitrarily control the switching element.

For these reasons, in recent years, a discharge lamp lighting device has been proposed which is relatively inexpensive and is capable of controlling switching elements, and for example, the configuration shown in FIG. 3 is known.

In the discharge lamp lighting device shown in FIG. 3, a start circuit 1 and a half-bridge type inverter circuit 2 are connected in series to a DC power source E, and vibration circuits 3 and 4 are connected to the output side of the inverter circuit 2. ing.

In the start circuit 1, a series circuit of a resistor R1 and a capacitor C1 is connected between both ends of a DC power source E, and a diode D1 and a trigger element Q3 are connected to a connection point of the resistor R1 and the capacitor C1. There is.

In the inverter circuit 2, the collector and emitter of the transistor Q1 which is a switching element and the collector and emitter of the transistor Q2 which is a switching element are connected in series between both terminals of the DC power source E, and these transistors Q1 and Q2 are connected. Free-wheeling diodes D2 and D3 are connected between the collector and the emitter of.

One end of the input winding CT1a of the driving current transformer CT1 is connected between the emitter of the transistor Q1 and the collector of the transistor Q2.
One end of CT1a is connected to the base of the transistor Q1 through the series circuit of the output winding CT1b and the resistor R2. In addition, the negative electrode of the DC power source E is connected to the transistor through the series circuit of the output winding CT1c of the current transformer CT1 and the resistor R3.
Connected to the base of Q2. Furthermore, the trigger element Q3 of the start circuit 1 is connected to the base of the transistor Q2.

A timer circuit 5 for the resistor R3 and the output winding CT1c of the current transformer CT1 is also connected. The reset circuit 6 is connected between the input terminal and the output terminal of the operational amplifier OP1, and the output terminal of the reset circuit 6 is connected to one input terminal of the operational amplifier OP1 forming the comparator. Further, a series circuit of a resistor R4 and a capacitor C2 is connected to the DC power source E1, and a connection point of the resistor R4 and the capacitor C2 is connected to an output terminal of the reset circuit 6. Furthermore, the DC power supply E1 is connected to a series circuit of a resistor R5 and a resistor R6, and the other input terminal of the operational amplifier OP1 is connected to the connection point of the resistor R5 and the resistor R6. Further, the output terminal of the operational amplifier OP1 is connected to the base of the transistor Q4, the collector of the transistor Q4 is connected to the base of the transistor Q2, and the emitter of the transistor Q4 is connected to the emitter of the transistor Q2.

The negative pole of the DC power source E is connected with series-cut capacitors C3 and C4.
A vibration circuit 3 is connected between the input winding CT1a and the input winding CT1a, and the vibration circuit 3 includes a choke coil L1 and a discharge lamp FL1.
Are connected in series, and a starting capacitor C5 is connected in parallel to the discharge lamp FL1. Meanwhile, capacitors
The vibration circuit 4 is connected between C4 and the input winding CT1a,
This vibration circuit 4 has a choke coil L2 and a discharge lamp.
FL2 is connected in series, and a starting capacitor C6 is connected in parallel to the discharge lamp FL2.

When a DC voltage is applied from the DC power source E, the capacitor C1 of the start circuit 1 is charged through the resistor R1 and when the voltage of the capacitor C1 reaches the set voltage of the trigger element Q3, the trigger element Q3. Breaks over, the charge charged in the capacitor C1 is input to the base of the transistor Q2 via the trigger element Q3, and the transistor Q2 is turned on.

When the transistor Q2 is turned on and a current flows in the input winding CT1a of the current transformer CT1, a voltage is induced in the output winding CT1c, the current is supplied to the base of the transistor Q2, and the transistor Q2 is Stay on. The base current is supplied to the transistor Q2, the reset circuit 6 operates, and the capacitor C2
Is charged.

Then, the charging voltage of the capacitor C2 becomes
When the midpoint potential set by R5 and resistor R6 is exceeded, the operational amplifier OP1 performs non-inverting output, supplies current to the base of transistor Q4 to turn on transistor Q4, and transistor Q2 is short-circuited between the base and emitter. Transistor Q2 is forced off. The ON period of the transistor Q2 is set by the time constants of the resistor R4 and the capacitor C2 of the timer circuit 5, and the voltage dividing resistance values of the resistors R5 and R6.

On the other hand, the transistor Q1 has an ON period set by the resonance time constants of the vibrating circuits 3 and 4,
Unless there is a change of 4, the ON period of the transistor Q1 is set to be constant.

[0014]

As described above, in the circuit shown in FIG. 3, only the ON period of the low-voltage side transistor Q2 is controlled, and the ON period of the high-voltage side transistor Q1 is always constant. Since the on-duty of Q1 and the transistor Q2 does not become 1: 1, it does not become a sine wave, but becomes a waveform with many harmonics as shown in FIG. Therefore, noise or the like may occur. There is also a problem that the loss on the high-voltage side transistor Q2 side is large.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a power supply device having a simple circuit configuration with an on-duty of 1: 1 to reduce loss and suppress noise generation. And

[0016]

SUMMARY OF THE INVENTION A power supply device of the present invention comprises a pair of switching elements connected in parallel between both ends of a DC power source and driven alternately on and off, and at least one of these switching elements. A resonance circuit connected in parallel with the switching element, a detection winding for detecting the current generated in the resonance circuit, and the current detected by the detection winding is fed back to the respective switching elements by magnetic coupling. It is provided with a current transformer having a positive feedback winding, and a magnetic energy control means connected to either one of the positive feedback windings to control magnetic energy.

[0017]

According to the present invention, the resonance circuit is provided with the detection winding for detecting the current flowing through the resonance circuit, and the bias energy for driving the switching element is secured in the positive feedback winding based on the current detected by the detection winding. In addition, the magnetic energy control means controls the magnetic energy of the positive feedback winding,
By controlling the other positive feedback winding by magnetic coupling, both switching elements are controlled and the frequency is varied, so that the on-duty of the switching element is 1:
Since it can be set to 1, the loss can be reduced, and the output current can be symmetrical in both positive and negative directions, a sine wave with less harmonic components can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power supply device of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a half-bridge type inverter circuit 11 is connected to a rectified and smoothed commercial AC power source or a DC power source E such as a battery.

In the inverter circuit 11, the drain and source of the field effect transistor Q11 which is a switching element and the drain and source of the field effect transistor Q12 which is a switching element are connected in series between both terminals of the DC power source E, These field effect transistors Q11,
There are parasitic diodes D11 and D12 between the drain and source of Q12, respectively.

A start circuit 12 is provided between the DC power sources E.
Are connected. In this start circuit 12, a series circuit of a resistor R11 and a capacitor C11 is connected between the DC power supplies E, and a diode D13 for discharging and a constant voltage element Q13 for trigger are connected to the connection point of these resistor R11 and capacitor C11. Are connected.

Further, the waveform improving circuit 13 is connected between the gate and the source of the field effect transistor Q11, and the waveform improving circuit is connected between the gate and the source of the field effect transistor Q12.
14 are connected. Then, the waveform improving circuit 13
It consists of R12, resistor R13 and capacitor C12, and the waveform improvement circuit 14 consists of resistor R14, resistor R15 and capacitor.
It is composed of C13.

The waveform improving circuit 13 has a current transformer CT.
The positive feedback winding CTa of the current transformer CT is connected to the positive feedback winding CTa of the current transformer CT.

Further, a resonance circuit 15 is connected between the drain and source of the field effect transistor Q12 via a detection winding CTc of the current transformer CT. The resonance circuit 15 includes a capacitor C14, a choke coil L11, and a discharge lamp FL connected in series, and a starting capacitor C15 is connected between both terminals of the discharge lamp FL.

A magnetic energy control means 16 is connected to the positive feedback winding CTb, and the magnetic energy control means 16 is composed of a voltage doubler rectifier circuit 17 and an output control circuit 18. The voltage doubler rectifier circuit 17 is composed of capacitors C16 and C17 and diodes D14 and D15. Further, in the output control circuit 18, the collector and the emitter of the transistor Q14 are connected between both terminals of the diode D17 via the resistor R16, and the variable resistor R17 is connected between the base and the emitter of the transistor Q14. A series circuit of a resistance R18 and a DC power supply E1 based on the DC power supply E, for example, is connected in parallel with the resistance R17.

Next, the operation of the embodiment shown in FIG. 1 will be described with reference to the waveform chart shown in FIG.

First, when the DC power supplies E and E1 are turned on, the capacitor C11 of the start circuit 12 is charged, and when the capacitor C11 reaches a predetermined voltage, the constant voltage element Q13 is triggered to turn on the field effect transistor Q12. Turn on. Then, the field-effect transistor Q12 and the field-effect transistor Q11 are alternately turned on and off, and the inverter circuit
11 starts oscillating.

After that, the choke coil L11 of the resonance circuit 15
And the capacitor C14 resonate with each other to generate a high voltage across the capacitor C15 and start the discharge lamp FL.

The resonance current flowing through the discharge lamp FL is detected by the detection winding CTc of the current transformer CT and is positively fed back to the positive feedback windings CTa and CTb, so that the waveform improving circuits 13 and 14 are improved.
At the gate voltage of each field effect transistor Q11, Q12 close to the square wave curve,
A gate voltage is applied to the field effect transistor Q12 to alternately turn it on and off.

Next, the operation of the magnetic energy control means 16 will be described.

The voltage doubler rectifier circuit 17 of the magnetic energy control means 16 rectifies the voltage in the direction in which the field effect transistors Q11 and Q12 are driven. Then, the output voltage of the voltage doubler rectifier circuit 17 is charged in the capacitor C17.
The electric charge charged in the capacitor C17 is consumed and controlled by the output control circuit 18. That is, by changing the resistance value of the variable resistor R17, the base current of the transistor Q14 is controlled, the resistance value between the collector and the emitter of the transistor Q14 is changed, and the capacitor C1
7. Control power consumption.

Therefore, the bidirectional magnetic energy of the current transformer CT is converted to a voltage by the voltage doubler rectifier circuit 17, the magnetic energy of the current transformer CT is consumed by the output control circuit 18, and the resistance value of the variable resistor R17 changes. As shown in Table 1, when the power consumption of the output control circuit 18 is large, the amount of magnetic energy also decreases and the saturation time of the current transformer CT is delayed, so that the oscillation frequency of each field effect transistor Q11, Q12 is delayed. And the output of the inverter circuit 11 increases. On the contrary, when the power consumption of the output control circuit 18 is small, the amount of magnetic energy increases and the current transformer
The saturation time of CT becomes faster, and each field effect transistor Q11
, The oscillation frequency of Q12 increases and the output of the inverter circuit 11 decreases.

[0033]

[Table 1] Then, as shown in FIG. 2, the field effect transistor Q11
Since both gate voltages of the field effect transistor Q12 and the field effect transistor Q12 are controlled, the field effect transistors Q11, Q12
Has a duty ratio of about 1: 1, the resonance current is also close to a sine wave, the harmonic components are reduced, and noise can be reduced. Therefore, the resistance value of the variable resistor R17 is changed to change the transistor Q1
By changing the impedance of 4, dimming can be performed linearly and with a sine wave.

Further, each field effect transistor
Since the waveform improving circuits 13 and 14 are provided in both Q11 and Q12, the loss is not increased in one of the field effect transistors Q11 and Q12, unbalance is not generated, and the reliability is improved. .

[0035]

According to the power supply device of the present invention, the bias energy for driving the switching element is secured in the positive feedback winding based on the current detected by the detection winding, and the positive feedback winding is controlled by the magnetic energy control means. By controlling the magnetic energy of, and also controlling the other positive feedback winding by magnetic coupling, both switching elements are controlled and the frequency is changed, so that the on-duty of the switching element can be set to 1: 1 and loss. In addition, the output current can be made symmetrical with respect to both positive and negative, so that it becomes possible to form a sine wave with few harmonic components.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of the above discharge lamp lighting device.

FIG. 3 is a circuit diagram showing a conventional discharge lamp lighting device.

FIG. 4 is a waveform diagram of the above discharge lamp lighting device.

[Explanation of symbols]

15 Resonance circuit 16 Magnetic energy control means CT Current transformer CTa, CTb Positive feedback winding CTc Detection winding E DC power supply Q11, Q12 Field effect transistor as switching element

Claims (1)

[Claims] 1. A pair of switching elements connected in parallel between both ends of a DC power source and alternately turned on and off, and connected in parallel to at least one of these switching elements. A resonance circuit, a detection winding for detecting a current generated in the resonance circuit, a current transformer having a positive feedback winding for returning the current detected by the detection winding to the respective switching elements by magnetic coupling, A power supply device, comprising: a magnetic energy control means connected to either one of the positive feedback windings to control magnetic energy.