JPH10341577A - Power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power unit which starts an inverter circuit without fail, and does not charge a large burden on a rush current preventive circuit, either. SOLUTION: The AC voltage of commercial AC power e is full-wave-rectified with a full wave rectifying circuit 3, and at power on, the rush current is suppressed by a rush current preventive resistance R1. A capacitor C3 is charged, and a thyristor Q1 is turned on, and a rush current preventive resistor R1 is bypassed. A transistor Q2 is chopped for boosting by a step-up chopper control circuit 6, and it is smoothed with a diode D1 and a capacitor C4 into DC voltage. The transistor Q3 and the transistor Q4 are operated by an inverter control circuit 8, and DC voltage is converted into AC voltage by an inverter circuit 7. The divided voltage of resistors R4 and R5 and the divided voltage of resistors R6 and R7 become roughly equal voltage, so this power unit starts the inverter circuit 7, too, without fail, preventing such trouble that the thyristor Q1 ceases to be turned on, due to the change of the rate of voltage rise, and keeping the output of a step-up chopper circuit 5 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power supply having a chopper circuit and an inverter circuit.

[0002]

2. Description of the Related Art Conventionally, as this type of power supply device, for example, a discharge lamp lighting device shown in FIG. 3 is known. In the discharge lamp lighting device shown in FIG. 3, a noise filter circuit 1 is connected to a commercial AC power supply e, and the noise filter circuit 1 has a capacitor C1, a common mode choke Tr1, and a capacitor C2. 1 is connected to a DC power supply conversion circuit 2.

In this DC power supply conversion circuit 2, an input terminal of a full-wave rectification circuit 3 such as a diode bridge is connected to a noise filter circuit 1, and an inrush current prevention circuit 4 is connected to an output terminal of the full-wave rectification circuit 3. Via the boost chopper circuit 5
Is connected.

The inrush current prevention circuit 4 has an inrush current prevention resistor R1 connected to the output side of the full-wave rectifier circuit 3 and an anode and a cathode of a thyristor Q1 connected in parallel to the inrush current prevention resistor R1. A parallel circuit of a resistor R2 and a capacitor C3 is connected between the gate and the cathode of Q1.

The step-up chopper circuit 5 includes a primary winding Tr2a of a transformer Tr2, a transistor Q2, and a resistor R3 between output terminals of the full-wave rectifier circuit 3 via an inrush current prevention resistor R1.
The series circuit of the transistor Q2 and the resistor
A series circuit of a diode D2 and a smoothing capacitor C4 is connected in parallel with R3. The transformer Tr2
The series resonance circuit is constituted by the primary winding Tr2a and the capacitor C4. A series circuit of a resistor R4 and a resistor R5 is connected between the output terminals of the full-wave rectifier circuit 3,
The connection point between R4 and resistor R5 is V
Connected to the HI terminal, a resistor R6 is connected in parallel with the capacitor C4.
And a series circuit of a resistor R7. A connection point between the resistors R6 and R7 is connected to a feedback VFB terminal of the boost chopper control circuit 6. A connection point between the transistor Q2 and the resistor R3 is connected to the boost chopper control circuit 6. Connected to the VCS terminal of the current sense amount, the boost chopper control circuit 6
Is connected to the gate terminal of the transistor Q2. The connection point between the diode D1 and the capacitor C4 is connected to the gate of the thyristor Q1 via the resistor R8. An error amplifier is connected in the VFB terminal, and controls the transistor Q2 of the boost chopper circuit 5 so that the voltage input to the VFB terminal is always constant.

The boost chopper circuit 5 is connected to a high frequency series resonance type half-bridge type inverter circuit 7 which is a frequency converter. In the inverter circuit 7, a transistor Q3 and a transistor Q4 are connected in series, and an inverter control circuit 8 is connected to gates of the transistor Q3 and the transistor Q4.
Further, a filament FLa of a fluorescent lamp FL as a discharge lamp is connected to both ends of the field effect transistor Q4 via a ballast choke L1 and a DC cut capacitor C6.
One end of FLb is connected, and these filaments FLa, FLb
Is connected to a start capacitor C7.

First, the AC voltage of the commercial AC power supply e is full-wave rectified by the full-wave rectifier circuit 3 through the noise filter circuit 1, and the rush current is suppressed by the rush current prevention resistor R1 when the power is turned on. That is, when power is turned on,
Since C3 is not charged, no voltage is applied to the gate of the thyristor Q1, and the thyristor Q1 maintains the off state, and the current from the full-wave rectifier circuit 3 flows through the inrush current prevention resistor R1.

Thereafter, when the capacitor C3 is charged, the thyristor Q1 is turned on, bypassing the inrush current prevention resistor R1.

Then, the transistor Q2 is chopped by the step-up chopper control circuit 6, the DC voltage full-wave rectified by the full-wave rectifier circuit 3 is stored in the transformer Tr2 when the transistor Q2 is turned on, and is converted when the transistor Q2 is turned off. Releases the energy of Tr2. Further, the voltage is smoothed by the diode D1 and the capacitor C4, and the voltage of the capacitor C4 becomes a DC voltage. According to the boost chopper circuit 5, the output voltage of the full-wave rectifier circuit 3 is directly applied to the transistor Q1.
And smoothing with the diode D1 and the capacitor C4, the impedance seen from the commercial AC power supply e side is increased, the power factor is improved, and the ripple can be reduced, so that the flicker of the fluorescent lamp FL can be reduced.

Further, the divided voltage of the resistors R4 and R5 is input to the boost chopper control circuit 6, and the output of the boost chopper circuit 5 is kept constant by the boost chopper control circuit 6 in accordance with the input fluctuation.

[0011]

However, in the conventional example shown in FIG. 3, when the power is turned on, the inrush current is reduced by the resistor R1. Due to the voltage drop, the voltage of the capacitor C4 becomes lower than the output of the full-wave rectifier circuit 3. And resistance
Since the voltage at the terminal VHI of the control circuit input from the connection point between R4 and R5 is apparently higher than the voltage at the terminal VFB of the control circuit input from the connection point between the resistors R6 and R7, the boost chopper If the boost rate by the circuit 5 is set to be constant, the boost rate of the boost chopper circuit 5 will decrease.

Therefore, the voltage of the capacitor C4 decreases and the inverter circuit 7 becomes difficult to start, and the gate voltage of the thyristor Q1 decreases.
Does not conduct, the resistor R1 may generate heat, and the inrush current prevention circuit 4 also has an undesirable problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a power supply device having a boost chopper circuit and an inverter circuit, which reliably starts the inverter circuit and does not impose a large burden on an inrush current prevention circuit. The purpose is to do.

[0014]

According to the present invention, there is provided a power supply unit having an inrush current prevention resistor for preventing an inrush current and a switching element connected in parallel to the inrush current prevention resistor and bypassing the inrush current prevention resistor. Prevention circuit, a chopper circuit that is connected via the inrush current prevention circuit and boosts the output voltage variable, an inverter circuit that converts the output of the chopper circuit into AC, and detects the voltage on the output side of the inrush current prevention circuit. A boost chopper control circuit that varies the output of the chopper circuit based on the detected voltage.
To detect the output voltage of the inrush current prevention circuit and vary the output of the chopper circuit based on the detected voltage,
Regardless of whether the current flows through the inrush current prevention resistor or the switching element of the inrush current prevention circuit, the output of the chopper circuit is controlled by the voltage after the voltage drops due to the impedance of the inrush current prevention resistor or the switching element. When the impedance of the prevention resistor or the switching element is different, it is possible to prevent the inverter circuit from operating or causing a problem in the inrush current prevention resistor.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the power supply device of the present invention will be described below with reference to the drawings. The parts corresponding to the conventional example shown in FIG.

In the discharge lamp lighting device shown in FIG. 1, a noise filter circuit 1 is connected to a commercial AC power supply e, and the noise filter circuit 1 has a capacitor C1, a common mode choke Tr1, and a capacitor C2. A DC power conversion circuit 2 is connected to the noise filter circuit 1.

In the DC power supply conversion circuit 2, an input terminal of a full-wave rectification circuit 3 such as a diode bridge is connected to the noise filter circuit 1, and an inrush current prevention circuit 4 is connected to an output terminal of the full-wave rectification circuit 3. Via the boost chopper circuit 5
Is connected.

The inrush current prevention circuit 4 includes an inrush current prevention resistor R1 connected to the full-wave rectifier circuit 3 and an anode and a cathode of a thyristor Q1 as a switching element connected in parallel to the inrush current prevention resistor R1. Thyristor
A parallel circuit of a resistor R2 and a capacitor C3 is connected between the gate and the cathode of Q1.

The boost chopper circuit 5 is connected to a series circuit of a primary winding Tr2a of a transformer Tr2, a transistor Q2 and a resistor R3 via a resistor R1 of the inrush current prevention circuit 4 and a thyristor Q1 as a switching element. A diode D2 is connected in parallel with the transistor Q2 and the resistor R3.
And a series circuit of a smoothing capacitor C4. Note that a series resonance circuit is configured by the primary winding Tr2a of the transformer Tr2 and the capacitor C4. A series circuit of a resistor R4 and a resistor R5 is connected between the inrush current prevention resistor R1 of the inrush current prevention circuit 4 and the output terminal of the full-wave rectifier circuit 3 via the thyristor Q1.
Is connected to the VHI terminal of the boost chopper control circuit 6, and a series circuit of the resistors R6 and R7 is connected in parallel to the capacitor C4. The connection point of the resistors R6 and R7 is connected to the boost chopper control circuit 6. VFB for feedback
The connection point of the transistor Q2 and the resistor R3 is connected to the VCS terminal of the current sense amount of the boost chopper control circuit 6, and the terminal V0 of the boost chopper control circuit 6 is connected to the gate terminal of the transistor Q2. The connection point between the diode D1 and the capacitor C4 is connected to the gate of the thyristor Q1 via the resistor R8. The boost chopper control circuit 6 is provided with a multiplier and an error amplifier. The VHI terminal is connected to one end of the multiplier, and the VFB terminal is connected to the inverting input terminal of the error amplifier. When the voltage input to the Vcs terminal reaches the voltage value, the transistor Q2 is turned off and the inductor is turned off.
The current flowing through L1 is controlled, and the transistor Q2 is kept off until the current flowing through the inductor L1 becomes 0, and is repeated even after the polarity is inverted. The boost ratio is set by the output of the multiplier and the voltage input to the VHI terminal, and controls the transistor Q2 of the boost chopper circuit 5 so that the voltage input to the VFB terminal is always constant.

The boost chopper circuit 5 is connected to a high frequency series resonance type half-bridge type inverter circuit 7 which is a frequency converter. In the inverter circuit 7, a transistor Q3 and a transistor Q4 are connected in series, and an inverter control circuit 8 is connected to gates of the transistor Q3 and the transistor Q4.
Further, a filament FLa of a fluorescent lamp FL as a discharge lamp is connected to both ends of the field effect transistor Q4 via a ballast choke L1 and a DC cut capacitor C6.
One end of FLb is connected, and these filaments FLa, FLb
Is connected to a start capacitor C7.

Next, the operation of the above embodiment will be described.

First, the AC voltage of the commercial AC power supply e is full-wave rectified by the full-wave rectifier circuit 2 via the noise filter circuit 1,
When the power is turned on, the rush current is suppressed by the rush current prevention resistor R1. That is, since the capacitor C3 is not charged when the power is turned on, no voltage is applied to the gate of the thyristor Q1. Electric current flows.

Thereafter, when the capacitor C3 is charged, the thyristor Q1 is turned on, bypassing the inrush current prevention resistor R1.

The transistor Q2 is chopped by the step-up chopper control circuit 6, and the full-wave rectified DC voltage is converted by the full-wave rectifier circuit 3 into a transformer when the transistor Q2 is turned on.
Energy is stored in Tr2, and the energy of transformer Tr2 is released when transistor Q2 is turned off. In addition, diodes
After smoothing by D1 and capacitor C4, the voltage of capacitor C4 becomes a DC voltage as shown in FIG.

Then, the transistor Q3 and the transistor Q4 are operated by the inverter control circuit 8, and the DC voltage is converted to the AC voltage by the inverter circuit 7.

According to the boost chopper circuit 5, the output voltage of the full-wave rectifier circuit 3 is directly chopped by the transistor Q2 and smoothed by the diode D1 and the capacitor C4. As a result, the inverter circuit 7 can also improve the power factor and reduce the ripple, so that the flicker of the fluorescent lamp FL can be reduced.

The voltage division of the resistors R4 and R5 and the resistor R6
And the divided voltage of the resistor R7 are input to the boost chopper control circuit 6, and the output of the boost chopper circuit 5 is kept constant by the boost chopper control circuit 6 in accordance with the input fluctuation.

Since the resistors R4 and R5 are located on the output side of the rush current prevention circuit 4, even when the rush current is reduced by the resistor R1 when the power is turned on, the thyristor Q1 is turned on and the rush current is turned on. Even when the prevention resistor R1 is bypassed, the voltage of the terminal VHI of the boost chopper control circuit 6 input from the connection point of the resistors R4 and R5 and the resistor
Since the voltage at the terminal VFB of the boost chopper control circuit 6 input from the connection point of R6 and the resistor R7 is equal,
Even at the start-up when a voltage drop occurs due to the inrush current prevention resistor R1, the boosting rate of the boost chopper circuit 5 does not decrease and the voltage of the capacitor C4 can be increased to the set voltage, thereby preventing the inverter circuit 7 from becoming difficult to start. I do. Also, since the gate voltage of thyristor Q1 can be prevented from lowering, the thyristor
Since Q1 is reliably turned on, it is possible to prevent current from continuing to flow through the inrush current prevention resistor R1, and prevent the inrush current prevention resistor R1 from generating heat.

[0029]

According to the power supply device of the present invention, the boost chopper control circuit detects the voltage on the output side of the inrush current prevention circuit and varies the output of the chopper circuit based on the detected voltage. Even if current flows through either the inrush current prevention resistor or the switching element of the protection circuit, the output of the chopper circuit is controlled by the voltage after the voltage drops due to the impedance of the inrush current prevention resistor or the switching element. Or, because the impedance of the switching element is different,
It can be prevented that the inverter circuit does not operate and that the rush current prevention resistor does not malfunction.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart showing the same operation.

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

[Explanation of symbols]

 5 Step-up chopper circuit 6 Step-up chopper control circuit 7 Inverter circuit Q1 Thyristor as switching element R1 Inrush current prevention resistor

Claims (1)

[Claims] 1. An inrush current prevention circuit having an inrush current prevention resistor for preventing an inrush current, a switching element connected in parallel with the inrush current prevention resistor, and a switching element for bypassing the inrush current prevention resistor. A chopper circuit that is connected to the inverter and converts the output of the chopper circuit into an alternating current; an inverter circuit that converts an output of the chopper circuit into an alternating current; a voltage on the output side of the inrush current prevention circuit, and the chopper circuit based on the detected voltage. And a step-up chopper control circuit for varying the output of the power supply.