JP2795387B2 - Power supply - Google Patents

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 which suppresses harmonic components and reduces switching loss and noise.

[0002]

2. Description of the Related Art A conventional power supply will be described with reference to FIG. The conventional power supply device shown in FIG.
Is connected to the full-wave rectifier circuit 1 via a filter inductor L1. A first capacitor C1 is connected between the output terminals of the full-wave rectifier circuit 1, and a diode D1 is connected in the forward direction to the positive electrode side of the full-wave rectifier circuit 1, and the full-wave rectifier circuit 1 The second capacitor C2 is connected to the wave rectifier circuit 1. A series circuit of a diode D2, an inductor L2 and a charging capacitor C3 is connected in parallel with the second capacitor C2.

Further, an inverter circuit 2 is connected between both terminals of the second capacitor C2.

The inverter circuit 2 includes a primary winding of an inverter transformer Tr1 between both terminals of a capacitor C2.
A series circuit of Tr1a and a transistor Q1 is connected, a capacitor C4 is connected in parallel with the primary winding Tr1a, and a feedback diode D3 is connected between the collector and the emitter of the transistor Q1.

[0005] The secondary winding of the inverter transformer Tr1
The filaments FLa and FLb of the discharge lamp FL are connected to Tr1b via a capacitor C5. Further, a starting capacitor C6 is connected to these filaments FLa and FLb.

On the other hand, the inverter transformer Tr1 has a detection winding Tr1c.
It is connected to the connection point between the inductor L2 and the charging capacitor C3 via D4.

Next, the operation of the circuit shown in FIG. 4 will be described with reference to the waveform chart shown in FIG.

[0008]

[0009] or not a, the inverter circuit 2, the capacitor C2
The switching of the DC voltage supplied from the transistor Q1 at a high frequency, the voltage resonated by the inductance of the primary winding Tr1a of the inverter transformer Tr1 and the capacitance of the capacitor C4 is transmitted to the secondary winding Tr1b, and the discharge lamp FL Supplied to And the capacitor C6 is the discharge lamp
The filaments FLa and FLb of the FL are preheated, and at the same time, the voltage generated by the capacitor C4 is applied to the discharge lamp FL.
Start and light up.

[0010]

[SUMMARY OF THE INVENTION However, in the embodiment shown in FIG. 4, the oscillating voltage component as compared to the actual voltage V C2 is voltage VC2a waveform of the second capacitor C2 shown in FIG. 5 <br /> Is big. Then, in the period TB, that abrupt spike current may arise from <br/>.

That is, when the transistor Q1 is turned on, the electromagnetic energy accumulated in the primary winding Tr1a of the inverter transformer Tr1 resonates with the resonance capacitor C4 when the transistor Q1 is turned off, and simultaneously applies a voltage to the secondary winding Tr2b. The discharge lamp FL is turned on by induction. However, upon polarity inversion of the resonance voltage of the capacitor C3, the terminal voltage of the capacitor C2, since flows through the inductor L2 and the diode D2 from the capacitor C3, the oscillating voltage is increased at a natural resonant frequency, the voltage of the capacitor C4 Get higher. At this time, since the transistor Q1 is turned on, the capacitor C4 is rapidly charged by the capacitor C2 due to the imbalance of the electrostatic energy due to the potential difference between the capacitors C2 and C4 , and a spike current is generated.

[0012] The spike current has a problem of causing switching loss to the transistor Q1 and increasing noise.

The present invention has been made in view of the above problems, and has as its object to provide a power supply device in which harmonics are reduced and switching loss and noise are reduced.

[0014]

A power supply apparatus according to the present invention includes a rectifier circuit for rectifying AC power of an AC power supply, a first capacitor connected between output terminals of the rectifier circuit, and a first capacitor. And a diode connected in a forward direction to the DC output of the rectifier circuit, a second capacitor connected between the output terminals of the rectifier circuit via the diode, and rectified by the rectifier circuit. A charging capacitor for charging a voltage equal to or lower than a peak value of the voltage;
And a control switching element connected in series with the charging capacitor and turned off when the oscillation switching element is turned on and turned on when the oscillation switching element is turned off. Is provided.

[0015]

According to the present invention, when the oscillation switching element is on, the control switching element is turned off, the charging capacitor is not charged and the charging capacitor is not discharged, and the oscillation switching element is turned off. Is turned on, the control switching element is turned on, and the charging capacitor, the diode, the control switching element, and the second
Since the current flows through the capacitor, the potential difference between the charging capacitor and the second capacitor is reduced, and since the inductance element is eliminated by using the control switching element, no resonance current is generated and the spike current is suppressed. To reduce harmonics,
Reduce switching loss and noise.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Parts corresponding to those of the conventional example shown in FIG.

As shown in FIG. 1, a full-wave rectifier circuit 1 is connected to a commercial AC power supply E via a filter inductor L1. Between the output terminals of the full-wave rectifier circuit 1,
A first capacitor C1 is connected, and a diode D1 is connected in the forward direction to the positive electrode side of the full-wave rectifier circuit 1. The full-wave rectifier circuit 1 via the diode D1 has a capacitance higher than that of the first capacitor C1. A small second capacitor C2 is connected.

Then, charging is performed in parallel with the second capacitor C2 at a voltage lower than the maximum instantaneous voltage value of the field effect transistor FET as a control switching element, the diode D2 and the full-wave rectifier circuit 1. The series circuit of the capacitor C3 is connected.

Further, an inverter circuit 2 is connected between both terminals of the second capacitor C2.

The inverter circuit 2 includes a primary winding of an inverter transformer Tr1 between both terminals of a capacitor C2.
Connect a series circuit of Tr1a and transistor Q1 as an oscillation switching element, connect a capacitor C4 in parallel with the primary winding Tr1a, and connect a feedback diode D3 between the collector and emitter of the transistor Q1. I do.

The secondary winding of the inverter transformer Tr1
The filaments FLa and FLb of the discharge lamp FL as loads are connected to Tr1b via a capacitor C5. Further, the filaments FLa and FLb have a starting capacitor.
Connect C6.

On the other hand, the inverter transformer Tr1 has a detection winding
Tr1c, this detection winding Tr1c is a diode D4
Is connected to both ends of the charging capacitor C3.

Further, resistors R1, R2, R3 and a zener diode ZD1 are connected to the gate of the field effect transistor FET.

Next, the operation of the circuit shown in FIG. 1 will be described.

First, when the power is turned on, full-wave rectification is performed by the full-wave rectifier circuit 1, and the first capacitor C1 and the second
A pulsating flow is applied to the condenser C2. Then, the inverter circuit 2 controls the switching of the DC voltage supplied from the second capacitor C2 by switching the transistor Q1 at a high frequency, and the voltage resonated by the inductance of the primary winding Tr1a of the inverter transformer Tr1 and the capacitance of the capacitor C4. It is induced in the secondary winding Tr1b and supplied to the discharge lamp FL. The current flowing through the capacitor C6 is the discharge lamp FL
Preheats the filaments FLa and FLb of
The generated voltage of C6 is applied to the discharge lamp FL, and the discharge lamp FL is started and turned on.

When the transistor Q1 is on, the voltage of the capacitor C4 does not rise, so that the Zener diode ZD1 is kept off, the field effect transistor FET is off, and the current flows through the charging capacitor C3. Not flowing.

On the other hand, when the transistor Q1 turns off, the voltage across the capacitor C4 increases. When the voltage exceeds the voltage set by the resistors R2 and R3, the Zener diode ZD1 turns on and the field effect transistor FET turns on. When the field effect transistor FET is turned on, the electric charge of the capacitor C3 is
The path of diode D2 and field effect transistor FET
To charge the second capacitor C2 .

Therefore, as in the prior art, the inductance
Does not use a scan, the vibration voltage higher than the charging voltage of the charging capacitor C3 in Figure 2, even among shown to period TB is lost, the instantaneous voltage is suppressed to below a predetermined value. Therefore, a rising spike current generated when the transistor Q1 is turned on can be prevented, and switching loss and noise can be reduced. Further, as shown in FIGS. 2 and 3, harmonics can be prevented as in the conventional example.

[0029]

According to the power supply device of the present invention, when the oscillation switching element is on, the control switching element is turned off, and the charging capacitor is not charged and the charging capacitor is not discharged. When the oscillating switching element is off, the control switching element is turned on, and current flows through the charging capacitor, the diode, the control switching element, and the second capacitor. Since the potential difference of the capacitor is reduced, and the inductance element is eliminated by using the control switching element, no resonance current is generated and the spike current can be suppressed, thereby reducing harmonics, reducing switching loss and noise. Can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart showing the same operation. (A) Voltage waveform diagram of first capacitor C1 (b) Voltage waveform diagram of second capacitor C2 (c) Output current and voltage waveform diagram

FIG. 3 is a waveform chart showing the same operation. (A) Current waveform diagram of transistor Q1 (b) Voltage waveform diagram of second capacitor C2

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

FIG. 5 is a waveform chart showing the same operation. (A) Voltage waveform diagram of the first capacitor C1 (b) Ideal voltage waveform diagram of the second capacitor C2 (c) Voltage waveform diagram of the second capacitor C2 (d) Output current and voltage waveform diagram

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Full-wave rectifier circuit 2 Inverter circuit C1 First capacitor C2 Second capacitor C3 Charging capacitor D1 Diode E Field-effect transistor FL as switching element for AC power FET Control discharge lamp as load Q1 Transistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02M 7/42-7/98 H05B 41/24

Claims (1)

(57) [Claims] 1. A rectifier circuit for rectifying AC power of an AC power supply, a first capacitor connected between output terminals of the rectifier circuit, and a rectifier circuit connected to the first capacitor for DC output of the rectifier circuit. And a second capacitor connected between the output terminals of the rectifier circuit via the diode, and charging for charging a voltage equal to or less than a peak value of the voltage rectified by the rectifier circuit. A single capacitor type inverter circuit having an oscillation switching element connected to the second capacitor and converting the output into a high-frequency output; and a series connected to the charging capacitor, which is turned off and on when the oscillation switching element is on. A power supply device comprising: a control switching element that is turned on at the time.