JPH08298780A - Power supply device - Google Patents

Abstract

PURPOSE: To inexpensively prevent temperature increase by reducing the output of an inverter means when the temperature increase is detected. CONSTITUTION: A transistor Q1 is oscillated by resonating with a parallel resonance circuit of a primary coil winding Tr 1 and a capacitor C2 of a resonance transformer Tr. In this case, as current flowing through afluorescent lamp FL increases, the charging time of capacitors C4 and C4 decreases, the oscillation frequency of the transistor Q1 increases and the output of an inverter circuit 2 decreases, thus making constant a voltage supplied to the fluorescent lamp FL. Also, when the temperature of the resonance transformer Tr or a reflux diode D1 increases, the voltages at the connection point between a thermistor R6 with positive temperature characteristics and a resistor R7 and that of the thermistor R6 with positive temperature characteristics and a resistor R9 decrease, the charging time of capacitors C4 and C6 decreases, the oscillation frequency of the transistor Q1 increases and the output of the inverter circuit 2 decreases, thus suppressing the heat generated by, for example, the resonance transformer Tr.

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 having an inverter circuit for converting into high frequency.

[0002]

2. Description of the Related Art Conventionally, as a power supply device of this kind, one used for a discharge lamp lighting device has been known.

In this discharge lamp lighting device, a resonance circuit is composed of a resonance capacitor and a resonance transformer, and a transistor having a freewheeling diode is switched based on the resonance of the resonance circuit and feedback of the output, and is converted into a high frequency by an inverter circuit. The fluorescent lamp is turned on at high frequency.

The core of the resonant transformer is brought into contact with the freewheeling diode and the transistor are mounted on the substrate.

[0005]

However, in the above-mentioned conventional structure, the temperature of the resonance transformer, the free wheeling diode, the transistor, etc. rises and the temperature of the substrate rises, especially for the end of the life of the fluorescent lamp or for thinning. When components are densely mounted by means such as, there is a problem that the temperature may become extremely high.

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 which can prevent temperature rise at low cost.

[0007]

According to a first aspect of the present invention, there is provided a power supply device, wherein a substrate and a core of a resonance transformer are mounted in close contact with one surface of the substrate so as to convert the power supply voltage into a high frequency and supply the load to an inverter. A temperature detecting means for detecting the temperature of the substrate by mounting a temperature sensitive element in the vicinity of the core; and a control means for decreasing the output of the inverter means when the temperature detecting means detects a temperature rise. It was done.

According to another aspect of the power supply device of the present invention, a board and a freewheeling diode that returns a resonance current when the switching element for switching is turned off are mounted on one surface of the board to convert the power supply voltage into a high frequency and supply the load. Inverter means, temperature detecting means for detecting the temperature of the substrate by mounting a temperature sensitive element in the vicinity of the free wheeling diode, and control means for lowering the output of the inverter means when the temperature detecting means detects a temperature rise. It is equipped with and.

[0009]

In the power supply device according to the present invention, the core of the resonance transformer of the inverter means is closely mounted on one surface of the substrate, and the temperature sensing element of the temperature detecting means is mounted in the vicinity of this core. When the temperature rise is detected, the output of the inverter means is reduced by the control means, so that the temperature rise of the resonance transformer and the substrate is prevented.

According to another aspect of the power supply device of the present invention, a free wheeling diode that returns a resonance current when the switching element for switching is turned off is mounted on one surface of the substrate, and a temperature sensitive element of the temperature detecting means is mounted near the free wheeling diode. When the temperature detecting means detects an increase in temperature, the control means reduces the output of the inverter means, thereby preventing an excessive rise in the temperatures of the free wheeling diode and the substrate.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power supply device of the present invention will be described below with reference to the discharge lamp lighting device shown in the drawings.

As shown in FIG. 1, an input terminal of a full-wave rectifier 1 for full-wave rectification is connected to a commercial AC power source E, and a smoothing capacitor C1 is connected to an output terminal of the full-wave rectifier 1.

An inverter circuit 2 as an inverter means is connected in parallel with the capacitor C1. This inverter circuit 2 connects the parallel circuit of the primary winding Tr1 of the resonance transformer Tr and the capacitor C2 for resonance and the collector and emitter of the transistor Q1 as a switching element in series, and the base of the transistor Q1 is a starting resistor. A freewheeling diode D1 for freewheeling is connected between the collector and the emitter while being connected to the positive electrode of the full-wave rectifier 1 via R1.

Further, the secondary winding Tr2 of the resonance transformer Tr is
The filaments FLa and FLb of the fluorescent lamp FL as a discharge lamp are connected via the primary winding CT1 of the current transformer CT. Further, a starting capacitor C3 is connected between the other ends of the filaments FLa and FLb.

The secondary winding CT2 of the current transformer CT
Control means 3 is formed and is connected between the base and emitter of the transistor Q1 via a capacitor C4. In addition, the series circuit of the drain and source of the capacitor C5 and the field effect transistor Q2 and the diode D2 are connected in parallel to the capacitor C4, and the diode D3, in parallel with the secondary winding CT2 of the current transformer CT. A series circuit of diode D4 and diode D5 is connected
Between the base and emitter of Q1, diode D6 and resistor
The series circuit of R2 is connected.

The temperature detecting means 4 is connected in parallel with the capacitor C1. This temperature detecting means 4
Resistor R3 and capacitor C6 in parallel with capacitor C1
Connected in series circuit, these resistors R3 and capacitor
The connection point of C6 is connected to the emitter of the transistor Q3 via the resistor R4, and the base of the transistor Q3 is connected to the positive electrode of the full-wave rectifier 1 via the resistor R5. The collector of the transistor Q3 is connected to the negative electrode of the full-wave rectifier 1 via the positive temperature characteristic thermistor R6 and the resistor R7 as the temperature sensitive element, and the base is the positive temperature characteristic thermistor R8 and the variable resistance as the temperature sensitive element. It is connected to the negative electrode of the full-wave rectifier 1 via R9, and the connection point of the positive temperature characteristic thermistor R6 and the resistor R7 is connected to the gate of the field effect transistor Q2 via the resistor R10.

The many components shown in FIG. 1 are mounted on the substrate 5 as shown in FIGS. 2 and 3. Also,
As shown in FIG. 2, the resonance transformer Tr has the core Tr3 of the resonance transformer Tr surface-mounted on the surface of the substrate 5, and the positive temperature characteristic thermistor R6 is provided on the back surface on which the core Tr3 of the resonance transformer Tr is located. As shown in FIG. 3, the free wheeling diode D1 is mounted by contacting the free wheeling diode D1 on the front surface of the substrate 5, and the positive temperature characteristic thermistor R8 is provided on the back surface on which the free wheeling diode D1 is located. .

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

First, the AC voltage of the commercial AC power source E is full-wave rectified by the full-wave rectifier 1 and smoothed by the capacitor C1. Then, the primary winding Tr1 of the resonance transformer Tr and the capacitor C2
The transistor Q1 is oscillated by resonating with the parallel resonance circuit of, and high-frequency alternating current is generated to turn on the fluorescent lamp FL. When the transistor Q1 is oscillated, the current flowing in the fluorescent lamp FL is fed back from the secondary winding CT2 of the current transformer CT, and when the current flowing in the fluorescent lamp FL increases, the charging time of the capacitors C4 and C5 is increased. It becomes short and increases the oscillation frequency of the transistor Q1,
The output of the inverter circuit 2 is lowered to make the voltage supplied to the fluorescent lamp FL constant. Positive temperature characteristic thermistor
When the temperature of R6 and the positive temperature characteristic thermistor R8 does not rise, the resistance values of the positive temperature characteristic thermistor R6 and the sex temperature characteristic thermistor R8 are low, so the connection point of the positive temperature characteristic thermistor R6 and the resistor R7, The voltage at the connection point of the positive temperature characteristic thermistor R8 and the resistor R9 becomes higher, and a predetermined voltage is applied to the gate voltage of the field effect transistor Q2, turning on the field effect transistor Q2 and turning on the capacitor C5 to the capacitor C4. It is connected in parallel.

On the contrary, when the current flowing through the fluorescent lamp FL decreases, the charging time of the capacitors C4 and C5 becomes longer and the oscillation frequency of the transistor Q1 is lowered,
The output of the inverter circuit 2 is increased to make the voltage supplied to the fluorescent lamp FL constant.

When the temperature of the resonance transformer Tr or the free wheeling diode D1 rises due to the rise of the ambient temperature or the end of the life of the fluorescent lamp FL, for example, the positive temperature characteristic thermistor R6 and the positive temperature characteristic are passed through the substrate 5. The temperature of the temperature characteristic thermistor R8 rises, the resistance values of the positive temperature characteristic thermistor R6 and the sex temperature characteristic thermistor R8 increase, and the voltage division ratio changes, so that the connection point of the positive temperature characteristic thermistor R6 and the resistor R7 becomes , Positive temperature characteristic thermistor R8
Since the voltage at the connection point of the resistor R9 and the voltage at the connection point of the resistor R9 become low, a predetermined voltage is not applied to the gate voltage of the field effect transistor Q2, the equivalent resistance value between the drain and source of the field effect transistor Q2 increases, and the capacitor C5 The apparent capacitance is reduced, the apparent combined capacitance of the capacitors C4 and C5 is reduced, the charging time of the capacitors C4 and C5 is shortened, the oscillation frequency of the transistor Q1 is increased, and the inverter circuit 2 Reduce the output,
It suppresses heat generation of the resonance transformer Tr, the free wheeling diode D1, etc., and suppresses heating of the board 5 and components on the board 5.

The positive temperature characteristic thermistors R6 and R8 are not limited to being provided in the resonance transformer Tr and the freewheeling diode D1, respectively, but may be in the resonance transformer Tr and the freewheeling diode D1.
The same effect can be obtained by either one provided on one side, the resonance transformer Tr or the freewheeling diode D1 interposed between the substrate 5 and the one which is insulated and closely attached to the resonance transformer Tr or the freewheeling diode D1. Obtainable.

In particular, when the device is not thin and the resonance transformer Tr is not in close contact with the substrate 5, the temperature of the substrate 5 can be reliably ensured by providing it on the substrate 5 opposite to the free wheeling diode D1. Can be detected.

[0024]

According to the power supply device of the first aspect, the core of the resonance transformer of the inverter means is closely mounted on one surface of the substrate, and when the temperature detecting means detects the temperature rise, the control means outputs the output of the inverter means. As a result, the temperature of the resonant transformer and the substrate can be prevented from rising excessively.

According to another aspect of the power supply device of the present invention, a free-wheeling diode that returns a resonance current when the switching element for switching is turned off is mounted on one surface of the substrate, and when the temperature detecting means detects the temperature rise, the control means is provided. Since the output of the inverter means is reduced by the above, it is possible to prevent the temperature of the free wheeling diode and the substrate from rising excessively.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a state in which a resonance transformer and a positive temperature coefficient thermistor are mounted on the same substrate.

FIG. 3 is an explanatory diagram showing a state in which a free wheel diode and a positive temperature coefficient thermistor are mounted on the same substrate.

[Explanation of symbols] 2 Inverter circuit as inverter means 3 Control means 4 Temperature detection means 5 Substrate D1 Reflux diode R6, R8 Positive temperature characteristic thermistor Tr as temperature sensing element Tr resonant transformer Q1 Transistor as switching element

Claims (2)

[Claims] 1. A substrate, an inverter means for closely mounting a core of a resonance transformer on one surface of the substrate, converting the power supply voltage into a high frequency and supplying it to a load, and a temperature sensitive device mounted in the vicinity of the core. A power supply device comprising: a temperature detecting means for detecting the temperature of the substrate; and a control means for decreasing the output of the inverter means when a temperature rise is detected by the temperature detecting means. 2. A substrate, an inverter means for circulating a resonance current when a switching element for switching is turned off is mounted on one surface of the substrate, an inverter means for converting a power supply voltage to a high frequency and supplying the load to the load, and the reflux diode. And a temperature detecting means for detecting the temperature of the substrate, and a control means for lowering the output of the inverter means when a temperature rise is detected by the temperature detecting means. And power supply.