JPH06113562A - Power supply - Google Patents

Abstract

PURPOSE:To provide a power supply in which noise is suppressed by setting a specific ON duty ratio through a simple circuitry. CONSTITUTION:A control means 15 oscillates at a frequency determined by a variable resistor R18, a resistor R19 and a capacitor C15 thus switching transistors Q13, Q14. Upon turn ON of the transistor Q14, pulsating charge current flows into a capacitor C12. The charging current flows through a control winding CT2 and a positive feedback winding CT2 and biases the base of transistor Q12 positively thus turning the Q12 ON. Current discharged from the capacitor C12 passes through the control winding CT2d and the positive feedback winding CT2c and biases the base of the transistor Q12 reversely thus turning the Q12 quickly; At the same time, positive bias current flows through a transistor Q11 thus turning the Q11 OFF quickly. Consequently, a choke coil L11 and the capacitor C12 in a resonance circuit 12 resonate to light a discharge lamp FL.

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 using a half-bridge type inverter circuit.

[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 which can control the switching element, and for example, the configuration shown in FIG. 4 is known.

In the discharge lamp lighting device shown in FIG. 4, a start circuit 1 and a half-bridge type inverter circuit 2 are cascade-connected 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 the 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. Furthermore, a series circuit of a resistor R4 and a capacitor C2 is connected to the control power supply E1, and the connection point of the resistor R4 and the capacitor C2 is connected to the output terminal of the reset circuit 6. Furthermore, the control power supply E1 is a resistor R5.
And a series circuit of a resistor R6 are connected, and the other input terminal of the operational amplifier OP1 is connected to a connection point of the resistors R5 and R6. Furthermore, the output terminal of the operational amplifier OP1 is connected to the base of the transistor Q4, and the collector of the transistor Q4 is connected to the base of the transistor Q2.
The emitter of transistor Q4 is connected to the emitter of transistor Q2.

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

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. 4, only the ON period of the transistor Q2 on the low voltage side is controlled, and the ON period of the transistor Q1 is always constant. Since the on-duty of Q2 does not become 1: 1, it does not become a sine wave.
As shown in, the waveform has many harmonics. Therefore,
It has a problem that noise may be generated.

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 and an on-duty of 1: 1 to suppress the generation of noise.

[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 control means for controlling the oscillation frequency of the switching element, a detection winding for detecting a current generated in the resonance circuit, and feedback to each of the switching elements. A positive feedback winding and a current transformer having a control winding that supplies positive and negative symmetrical pulse currents to the respective switching elements based on the output of the control means, and the currents of the detection winding and the control winding are The oscillating frequency of the switching element is varied by combining them.

[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 ON / OFF duty of the switching element is set to 1: 1 by controlling ON / OFF timing in the control winding based on the positive / negative symmetrical pulse current generated by the control means and controlling the respective switching elements to change the frequency. Since it can be set and the output current can be made symmetrical with respect to both positive and negative, it becomes possible to form a sine wave with few harmonic components.

[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.

The inverter circuit 11 has a DC power source E
Transistor Q11 which is a switching element between both terminals of
Is connected in series with the collector and emitter of the transistor Q12, which is a switching element, and between the collectors and emitters of these transistors Q11 and Q12, diodes D11 and D12 for free-flowing connection are respectively connected. A resistor R11 is connected between the base and emitter of the transistor Q11, and a resistor R12 and a diode D13 are connected to the base. Furthermore, a resistor R13 is placed between the base and emitter of the transistor Q12.
And a resistor R14 and a diode D14 are connected to the base.

A capacitor C11, a discharge lamp FL, a choke coil L11 and a detection winding CT2a of a current transformer CT2 are connected in series between the collector and the emitter of the transistor Q11, and between the terminals of the discharge lamp FL. A capacitor C12 for starting is connected, and the capacitor C11, the discharge lamp FL, the choke coil L11, and the like form a resonance circuit 12. And transistor Q1 via resistor R12
The positive feedback winding CT2b of the current transformer CT2 is connected between the base and emitter of 1, and the transistor via the resistor R14 is connected.
The positive feedback winding CT2c of the current transformer CT2 is connected between the base and emitter of Q12. This positive feedback winding
The CT2c has a characteristic opposite to that of the positive feedback winding CT2b, and supplies currents in different directions to the bases of the transistors Q11 and Q12.

In addition, the current transformer CT2 has a control winding CT.
2d is provided, and the control winding CT2d is connected to the control means 15.

Then, the control means 15 controls the control winding CT2d.
To the control winding CT2d and the capacitor C12, a diode D15 and an NPN transistor Q13 collector and emitter are connected in series. In addition, diode D15 and control winding
A series circuit of a collector and an emitter of a diode D16 and a PNP type transistor Q14 is connected to a connection point of CT2d. The base of transistor Q13 is a resistor
Connected to astable multivibrator 16 via R15 and capacitor C13. Similarly, transistor Q14
The base of is connected to astable multivibrator 16 via resistor R16 and capacitor C14.

Further, this astable multivibrator 16
Is a general-purpose timer IC17 such as model number TA7555P manufactured by Toshiba Corporation, resistor R17, variable resistor R18, resistor
R19, capacitor C15 and capacitor C20 are connected. The astable multivibrator 16 is a time constant circuit composed of a variable resistor R18, a resistor R19 and a capacitor C15 and oscillates at a duty ratio of about 1: 1.
In addition, an astable multivibrator is provided by the variable resistor R18.
16 oscillation frequencies can be changed.

Furthermore, this astable multivibrator 16
Is connected to the DC power supply E1.

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 general-purpose timer IC 17 is activated, and the control means 15 oscillates at a frequency determined by the time constants of the variable resistor R18 and the resistor R19 and the capacitor C15, and the control is performed. Transistor from the output of means 15
The drive signals of Q13 and Q14 are output, and the transistors Q13 and Q14
Q14 starts switching operation alternately.

When the transistor Q14 is turned on, the DC power source E causes the transistor Q14 and the diode D1 to be turned on.
A pulsed charging current flows through the capacitor C12 via 6 and the control winding CT2d. Then, this charging current is transferred from the positive feedback winding CT2c through the control winding CT2d to the transistor Q1.
Supplied as a positive bias current to the base of 2. Also,
This positive bias current activates transistor Q12,
A current flows from the DC power source E through the capacitor C11, the capacitor C12, the choke coil L11, the detection winding CT2a of the current transformer CT2 and the transistor Q12, and the current transformer
The positive feedback current from the positive feedback winding CT2c based on the current detected by the detection winding CT2a of CT2 causes the second transistor Q12
Turns on rapidly.

Then, when the transistor Q14 turns off and then the transistor Q13 turns on, the capacitor C1 is turned on.
The charge of 2 is discharged through the control winding CT2d, the diode D15 and the transistor Q13. The discharge current from the capacitor C12 is applied as a reverse bias from the positive feedback winding CT2c to the base of the transistor Q12 via the control winding CT2d, and this reverse bias causes the transistor Q12 to rapidly turn off.

Further, this discharge current is simultaneously applied to the transistor.
It becomes the positive bias current that starts Q11, and the positive feedback winding CT2b
The positive feedback current from Q causes transistor Q11 to turn on rapidly, and the charging current also reverse biases transistor Q11, turning it off.

Therefore, the transistors Q11 and Q12 are controlled by the charging / discharging current of the capacitor C12 by the on / off operations of the transistors Q13 and Q14 to perform the switching operation. Due to this switching operation, the resonance circuit
The 12 choke coils L11 and the capacitor C12 resonate,
A high voltage is generated across capacitor C12,
Start FL and turn it on. In addition, the choke coil at this time
The natural frequency of L11 and capacitor C12 is
It is set lower than the oscillation frequency of C17. Further, by changing the oscillation frequency of the general-purpose timer IC17 by changing the charging / discharging current cycle of the capacitor C12, the frequency of the inverter circuit 11 changes, and the output power of the discharge lamp FL can be changed linearly.

As shown in FIG. 3, the output signal of the general-purpose IC timer 17 oscillates at a duty ratio of about 1: 1 and the duty ratio of the transistors Q11 and Q12 is about 1: 1.
Since the resonance current is close to a sine wave, the harmonic components are reduced and noise can be reduced. Also, two transistors Q11
, Q12 are forcibly turned off alternately by the control winding CT2d, so switching loss can be reduced and two transistors
The imbalance between Q11 and Q12 will also disappear.

[0033]

According to the power supply device of the present invention, the resonance circuit is provided with the detection winding for detecting the current flowing through the resonance circuit,
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 on / off timing is controlled by the control winding based on the positive / negative symmetrical pulse current generated by the control means. The on-duty of the switching element is set to 1: by controlling the switching element and varying the frequency.
Since it can be set to 1 and the output current can be symmetrical in both positive and negative, a sine wave with few harmonic components can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a power supply device of the present invention.

FIG. 2 is a waveform diagram of the above power supply device.

FIG. 3 is a waveform diagram of the above power supply device.

FIG. 4 is a circuit diagram showing a conventional power supply device.

FIG. 5 is a waveform diagram of the above power supply device.

[Explanation of symbols]

 12 Resonant circuit 15 Control means CT2 Current transformer CT2a Detection winding CT2b, CT2c Positive feedback winding CT2d Control winding E DC power supply Q11, Q12 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 control means for controlling the oscillation frequency of the switching element, a detection winding for detecting a current generated in the resonance circuit, a positive feedback winding for feeding back to each of the switching elements, and an output of the control means. And a current transformer having a control winding that supplies positive and negative symmetrical pulse currents to the respective switching elements, and the oscillation frequency of the switching element is varied by combining the currents of the detection winding and the control winding. A power supply device characterized by: