JPH07274490A - Power unit, and lamp lighting device, and illuminator - Google Patents

Abstract

PURPOSE:To provide a lamp lighting device which prevents an overcurrent from flowing to a chopper circuit even if short circuit occurs on the secondary side of a choke coil. CONSTITUTION:If a current flowing through a lamp L increases more than necessary, the voltage of a resistor R5. goes up, and a transistor Q2 is turned on, and a light emitting diode LED 1 lights, and a control means 3 controls the operation of a field effect transistor Q1 so as to lower or stop the output of a chopper circuit 2. In case that wire breaking occurs on the side of the secondary wiring Tr1b, the voltage of a capacitor C5 drops, and the base current of a transistor Q3 vanishes, and the transistor Q3 is turned off to stop bypassing the base current of the transistor Q4. The current flowing through the side of a light emitting diode LED1 is bypassed by turning on the transistor Q4 so as to prevent the control circuit 3 from controlling the chopper circuit 2 by overcurrent.

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, a lamp lighting device, and a lamp lighting device which can surely control the output of a chopper circuit even if a detection winding magnetically coupled to a choke coil of a chopper circuit is short-circuited. Related to a lighting device.

[0002]

2. Description of the Related Art As a conventional lamp lighting device of this type, for example, a structure shown in FIG. 5 is known.

As shown in FIG. 5, an input terminal of a full-wave rectifier 1 such as a diode bridge is connected to a commercial AC power source E, and a thyristor Th1 is connected in parallel to an output terminal of the full-wave rectifier 1. A resistor R1 and a smoothing capacitor C1 are connected.

Then, between both terminals of this capacitor C1,
The chopper circuit 2 is connected. This chopper circuit 2
Is connected in parallel to the capacitor C1 to the drain and source of the field effect transistor Q1 as a switching means and the diode D1, and across the diode D1 the primary winding Tr1a as the choke coil of the transformer Tr1 and the capacitor C2. It is configured by connecting a series circuit.

A lamp L formed of a general light bulb such as an incandescent light bulb having a filament as a load is connected between both terminals of the capacitor C2.

Further, the control means 3 is connected to the secondary winding Tr1b as a detection winding of the transformer Tr1 via a diode D2 and a capacitor C3. The control means 3 is driven by the DC power source E1 and is connected to the primary winding Tr2a of the control transformer Tr2 that controls the chopper circuit 2. The secondary winding Tr2b of the control transformer Tr2 is connected between the gate and the source of the field effect transistor Q1.

In addition, a resistor is connected in parallel with the capacitor C1.
A series circuit of R2 and Zener diode ZD1 is connected,
Capacitor C4 is connected in parallel with this Zener diode ZD1.
Are connected. Furthermore, the resistor R3, the light emitting diode LED1 and the transistor are connected between both terminals of the capacitor C4.
A series circuit of collector and emitter of Q2 is connected.
Further, a resistor R4 and a resistor R5 are connected to the transistor Q2.

Then, the voltage of the commercial AC power source E is full-wave rectified by the full-wave rectifier 1 and smoothed by the capacitor C1. The control means 3 controls the field effect transistor Q1 to accumulate a predetermined charge in the capacitor C2 and turn on the lamp L.

When the current flowing through the primary winding Tr1a of the transformer Tr1 increases, the voltage of the secondary winding Tr1b increases and the voltage of the capacitor C3 increases, and the control means 3 controls the field effect transistor Q1. , The output of the chopper circuit 2 is reduced.

On the other hand, when the current flowing through the lamp increases more than necessary, the voltage of the resistor R5 rises, the transistor Q2 turns on and the light emitting diode LED1 lights up, and the control means 3 controls the operation of the field effect transistor Q1. The output of the chopper circuit 2 is lowered or stopped.

Further, when the current to the lamp L rises above a predetermined value, the lamp L is melted and the chopper circuit 2 is protected from abnormal oscillation.

[0012]

However, in the above embodiment, when the secondary winding Tr1b side is short-circuited, the inductance value of the primary winding Tr1a becomes 0 and the current increases, Since the transistor Q2 operates, the voltage of the chopper circuit 2 is lowered, and the lamp L is not melted. Therefore, an excessive current continues to flow in the secondary winding Tr1b, which may cause smoke or burn.

The present invention has been made in view of the above problems, and a power supply device, a lamp lighting device, and a lighting device that prevent an overcurrent from continuing to flow in a chopper circuit even if a short circuit occurs on the secondary side of a choke coil. The purpose is to provide.

[0014]

According to a first aspect of the present invention, there is provided a power supply device in which a load is connected to an output end of a chopper circuit having a switching means and a choke coil, and the detection winding is magnetically coupled to the choke coil. A control means is connected to the detection winding to decrease the output of the chopper circuit when the output current exceeds a predetermined value, and when the output current of the chopper circuit exceeds a predetermined value, the load is opened to release the load. In the power supply device for stopping the output of the chopper circuit, short-circuit detection means for detecting a short circuit of the detection winding is provided, and when the short-circuit detection means detects a short circuit of the detection winding, the control means controls the control means. Is to stop the operation of lowering the output of the chopper circuit.

According to a second aspect of the present invention, in the power source apparatus according to the first aspect, the short-circuit detection means includes a detection winding magnetically coupled to the choke coil. The short circuit of is detected.

According to a third aspect of the present invention, in the power source apparatus according to the first or second aspect, voltage detecting means for detecting the output voltage of the chopper circuit is provided, and when the voltage detecting means detects a voltage equal to or higher than a predetermined value. The control means controls the output of the chopper circuit to either stop or decrease.

According to a fourth aspect of the present invention, there is provided a lamp lighting device in which the load of the power supply unit according to any one of the first to third aspects is a lamp having a filament.

According to a fifth aspect of the present invention, there is provided the lamp lighting device according to the fourth aspect in which a lighting fixture is provided.

[0019]

In the power supply device according to the present invention, the short-circuit detection means detects a short circuit in the detection winding, and when the short-circuit detection means detects a short circuit in the detection winding, the control means lowers the output of the chopper circuit. In order to stop the operation, the load is opened due to the overcurrent, the overcurrent is prevented from continuing to flow in the detection winding, and smoking and burning are prevented.

According to a second aspect of the present invention, in the power source apparatus according to the first aspect, the short-circuit detecting means detects a short circuit in the detection winding by the detection winding magnetically coupled to the choke coil. It is a simple structure.

According to a third aspect of the present invention, in the power source apparatus according to the first or second aspect, when the voltage detecting means detects that the output voltage of the chopper circuit is equal to or higher than a predetermined value, the control means outputs the output of the chopper circuit. Since it is controlled to either stop or decrease, smoke and burn can be prevented more reliably.

In the lamp lighting device according to the fourth aspect, since the load of the power supply device according to any one of the first to third aspects is a lamp having a filament, the filament of the lamp is melted to prevent smoking and burning.

In the lighting device according to the fifth aspect, since the lighting device is provided in the lamp lighting device according to the fourth aspect, the filament of the lamp is melted to prevent smoking and burning.

[0024]

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

The circuit shown in FIG. 1 is housed in a device body (not shown).

As shown in FIG. 1, an input terminal of a full-wave rectifier 1 such as a diode bridge is connected to a commercial AC power source E, and a thyristor Th1 is connected in parallel to an output terminal of the full-wave rectifier 1. The connected resistor R1 and the smoothing capacitor C1 are connected.

Then, between both terminals of this capacitor C1,
The chopper circuit 2 for step-down is connected. In this chopper circuit 2, the drain and source of a field effect transistor Q1 as switching means and a diode D1 are connected in parallel to a capacitor C1, and a primary winding Tr1a as a choke coil of a transformer Tr1 is connected between both ends of this diode D1. And a series circuit of a capacitor C2 is connected.

A lamp L having a filament as a load is connected between both terminals of the capacitor C2.

Further, the control means 3 is connected to the secondary winding Tr1b as a detection winding of the transformer Tr1 via a diode D2 and a capacitor C3. The control means 3 is driven by the DC power source E1 and is connected to the primary winding Tr2a of the control transformer Tr2 that controls the chopper circuit 2. The secondary winding Tr2b of the control transformer Tr2 is connected between the gate and the source of the field effect transistor Q1.

Further, in parallel with the capacitor C1, a resistor
A series circuit of R2 and Zener diode ZD1 is connected,
Capacitor C4 is connected in parallel with this Zener diode ZD1.
Are connected. Further, a series circuit of a collector and an emitter of a resistor R3, a light emitting diode LED1 photocoupled to a phototransistor PTr, and an overcurrent detection transistor Q2 is connected between both terminals of the capacitor C4. Further, a resistor R4 and a resistor R5 are connected to the transistor Q2.

Further, the primary winding Tr1a and the secondary winding Tr1b
Detection winding Tr as a short-circuit detection means magnetically coupled to
1c, a diode D3 and a capacitor C5 are connected to the detection winding Tr1c, the negative side of the capacitor C5 is connected to the negative side of the full-wave rectifier 1, and the positive side is connected to the base of the transistor Q3 via a resistor R6. It is connected. The emitter of the transistor Q3 is connected to the negative electrode of the full-wave rectifier 1, the collector is connected to the connection point of the primary winding Tr1a of the transformer Tr1 and the lamp L via the resistor R7, and also via the resistor R8. It is connected to the base of the transistor Q4, the collector of the transistor Q4 is connected to the connection point of the resistor R2 and the capacitor C4 via the resistor R9, and the emitter is connected to the negative electrode of the full-wave rectifier 1.

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

First, the voltage of the commercial AC power source E is full-wave rectified by the full-wave rectifier 1 and smoothed by the capacitor C1. Control means 3
The field effect transistor Q1 is controlled by
A predetermined charge is accumulated in C2 and the lamp L is turned on.

When the current flowing through the primary winding Tr1a of the transformer Tr1 increases, the voltage of the secondary winding Tr1b increases and the voltage of the capacitor C3 increases, and the control means 3 controls the field effect transistor Q1. , The output of the chopper circuit 2 is reduced.

On the other hand, when the current flowing through the lamp L increases more than necessary, the voltage of the resistor R5 rises, the transistor Q2 turns on, the light emitting diode LED1 lights up, and the control means 3 controls the operation of the field effect transistor Q1. Then, the output of the chopper circuit 2 is reduced or stopped. In this case, since the voltage is induced in the detection winding Tr1c, the capacitor C5 becomes a predetermined voltage, the base current is supplied to the transistor Q3, the transistor Q3 is turned on, and the base current of the transistor Q4 is bypassed. Then, the transistor Q4 is turned off so that a current flows to the light emitting diode LED1 side.

Further, when the current to the lamp L rises above a predetermined value, the lamp L is melted and the chopper circuit 2 is protected from abnormal oscillation.

When a disconnection occurs on the side of the secondary winding Tr1b, the voltage of the capacitor C5 drops, and the base current of the transistor Q3 disappears as shown in FIG. 2 (b).
As shown in (c), the transistor Q3 is turned off to stop bypassing the base current of the transistor Q4, and as shown in FIG. 2 (a), the transistor Q4 is turned on and the current flowing to the light emitting diode LED1 side is reduced. Bypassing prevents the control means 3 from controlling the chopper circuit 2 due to overcurrent.

Therefore, even if the current on the side of the secondary winding Tr1b is short-circuited, the protection due to the overcurrent is not performed, so that the lamp L
Since the state where an overcurrent is applied to the lamp is maintained, the lamp L
Filament breaks and the secondary winding Tr1b side heats up,
It is possible to prevent smoking and burning.

Furthermore, if a wire break occurs on the output side,
The voltage of the capacitor C5 drops, and the base current of the transistor Q3 disappears as shown in FIG. 3 (b).
As shown in Fig. 3, the transistor Q3 is in the off state, bypassing the base current of the transistor Q4, and turning off the transistor Q4 as shown in Fig. 3 (a) so that the current flows to the light emitting diode LED1 side. Means 3 control the chopper circuit 2.

Next, another embodiment will be described with reference to FIG.

The embodiment shown in FIG. 4 is different from the embodiment shown in FIG. 1 in that the voltage detecting means 4 is provided between both terminals of the capacitor C2.
The voltage detecting means 4 controls the switch SW connected in series to the DC power source E1.

When a disconnection occurs on the side of the secondary winding Tr1b, the voltage of the voltage detecting means 4 rises and the switch SW of the DC power source E1 is opened, so that the control means 3 is stopped and the chopper is stopped. The operation of the circuit 2 can be stopped.

[0043]

According to the power supply device of the present invention, the short-circuit detecting means detects the short-circuit of the detection winding, and when the short-circuit detecting means detects the short-circuit of the detection winding, the control means causes the chopper circuit to operate. Since the operation of lowering the output of is stopped, the load is prevented from opening due to the overcurrent, the overcurrent is prevented from continuing to flow in the detection winding, and smoking and burning can be prevented.

According to the power supply device of the second aspect, in addition to the power supply device of the first aspect, the short-circuit detection means detects the short-circuit of the detection winding by the detection winding magnetically coupled to the choke coil. Therefore, the configuration can be simple.

According to the power supply device of claim 3, in addition to the power supply device of claim 1 or 2, when the voltage detection means detects that the output voltage of the chopper circuit is a predetermined value or more,
Since the control means controls the output of the chopper circuit to either stop or decrease, smoke and burn can be prevented more reliably.

According to the lamp lighting device of the fourth aspect,
Since the load of the power supply device according to any one of claims 1 to 3 is a lamp having a filament, it is possible to prevent the filament of the lamp from being melted and to prevent smoking and burning.

According to the lighting device of the fifth aspect, since the lighting device is provided in the lamp lighting device of the fourth aspect, the filament of the lamp can be melted and blown off to prevent smoking and burning.

[Brief description of drawings]

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

FIG. 2 is a voltage waveform diagram showing an operation when the secondary side of the same is short-circuited.

FIG. 3 is a voltage waveform diagram showing an operation when the output side is short-circuited.

FIG. 4 is a circuit diagram showing an embodiment of a lamp lighting device of another embodiment of the same.

FIG. 5 is a circuit diagram showing a conventional lamp lighting device.

[Explanation of symbols]

 3 Control means L Lamp as load Q1 Field effect transistor as switching means Tr1a Primary winding as choke coil Tr1b Secondary winding as detection winding Tr1c Detection winding as short-circuit detection means

Claims (5)

[Claims] 1. A load is connected to an output end of a chopper circuit having a switching means and a choke coil, a detection winding is provided by being magnetically coupled to the choke coil, and a control means is connected to the detection winding. When the output current exceeds a predetermined value, the output of the chopper circuit is reduced,
In a power supply device that opens the load and stops the output of the chopper circuit when the output current of the chopper circuit becomes a predetermined value or more, short-circuit detection means for detecting a short circuit of the detection winding is provided, and this short-circuit detection means A power supply device characterized in that, when a short circuit of the detection winding is detected, the control means stops the operation of reducing the output of the chopper circuit. 2. The power supply according to claim 1, wherein the short-circuit detection means includes a detection winding magnetically coupled to the choke coil, and the detection winding detects a short circuit in the detection winding. apparatus. 3. A voltage detecting means for detecting the output voltage of the chopper circuit is provided, and when the voltage detecting means detects a voltage equal to or higher than a predetermined value, the control means controls the output of the chopper circuit to either stop or decrease. The power supply device according to claim 1, wherein the power supply device is provided. 4. A lamp lighting device, wherein the load of the power supply device according to claim 1 is a lamp having a filament. 5. A lighting device comprising the lamp lighting device according to claim 4 and a lighting fixture.