JPS63245276A - Power converter - Google Patents

Abstract

PURPOSE:To reduce a cost and miniaturize a device and enhance the efficiency, by detecting the ambient temperature of a load or the like, and by controlling the ON/OFF-frequency and duty of an inverter variably according to the ambient temperature. CONSTITUTION:An electric-discharge lamp lighting equipment is provided with a DC power-supply circuit 1, an inverter circuit 2, a dimming change-over circuit 3, an overall light starting circuit 4, a soft start circuit 5, a power-supply voltage/temperature compensating circuit 6, a non-load stop circuit 7, and a switching improvement circuit 8. By varying a reset resistor VR with the inverter circuit 2, its oscillation frequency can be varied. Besides, by controlling the ON/OFF- frequency and duty of a transistor Tr 1 variably according to the ambient temperature of the equipment, output frequency is varied, and to the fluorescent lamp FL of a load, output according to the ambient temperature can be fed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power conversion device that converts DC power to AC power.
The present invention relates to a power conversion device suitable as a discharge lamp lighting device that lights with AC power of 20 to 100 kHz, for example.

[Prior Art] Discharge lamps such as fluorescent lamps have reduced starting performance and light output at low temperatures. Therefore, it is desirable for a device for lighting such a discharge lamp to be able to vary its output in accordance with changes in ambient temperature.

Conventionally, this type of equipment uses a series regulator, switching regulator, etc. as a DC power supply.
This DC power supply was given temperature characteristics to control the input terminals of the inverter, which in turn controlled the inverter's output.

[Problems to be Solved by the Invention] Therefore, conventional devices require power supply circuits such as series regulators and switching regulators, and have the disadvantages of having a large number of parts, high cost, large size, and low efficiency. .

The present invention was made in view of the problems of the conventional type described above, and is capable of changing output according to changes in ambient temperature, has fewer parts than conventional types of the same type, is low in cost, small in size, and has a high cost. The purpose is to provide an efficient power conversion device.

[Means for Solving the Problems] In order to achieve the above [1], the present invention detects the ambient temperature of the device or the load, and turns on/off the main switching element forming the inverter δ-groove in response to this detection signal. The off frequency and/or on/off duty are variably controlled.

[Operations and Effects] This type of inverter generally has a reactance element such as a resonant circuit or an output transformer connected to the output end. Also, when a discharge lamp is used as a load, a glue actance element such as an inductor is connected as a ballast of the discharge lamp.

Therefore, as mentioned above, by variably controlling the on/off frequency and/or duty of the main switching element according to the ambient temperature of the device, the output frequency is varied and an output corresponding to the ambient temperature is supplied to the load. be able to. Therefore, when the device of the present invention is used as a discharge lamp lighting device, by increasing the output when the temperature is low, it is possible to improve the starting characteristics of fluorescent lamps, etc. and ensure the light output when lighting. .

Further, since the device of the present invention does not require a stabilizing power supply circuit for stabilizing the DC input, it has fewer parts than the conventional type, and is lower in cost, smaller in size, and more efficient.

The output of the inverter can be designed to the minimum necessary, and from this point of view as well, miniaturization and cost reduction can be achieved.

[Example] The present invention will be described in detail below using the drawings.

FIG. 1 shows a block circuit of a discharge lamp lighting device according to an embodiment of the present invention. The device in the figure includes a DC power supply circuit 1, an inverter circuit 2, a dimming switching circuit 3, an all-light starting circuit 4, a soft start circuit 5, a power supply voltage/temperature compensation circuit 6, a no-load stop circuit 7, and a switching improvement circuit. 8.

The DC power supply circuit 1 includes a full-wave rectifier circuit DB and a smoothing capacitor C4, and has a smoothing angle of 2i from an AC power supply (not shown).
9i, generate voltage.

The inverter circuit 2 uses a semi-E class self-excited single transistor inverter circuit, and has an LC resonance circuit of an inductor Ll and a capacitor C1 connected between the collector of the switching transistor Tri and the positive terminal a of the DC power supply, and a current limiting circuit ( A series circuit of an inductor L2 (for ballast) and a fluorescent lamp FL as a load is connected, and a feedback winding L2f' provided in the inductor L2 is connected to the base of the transistor Tri at one end via a series circuit of a capacitor C3 and an inductor L3. The other end is connected to the negative terminal of the DC power supply. In addition, a variable resistor VR is connected between the base of the transistor Tri and the negative side terminal of the DC power supply, and the transistor Tr
The emitter of i is connected to the negative terminal of the DC power supply via a diode D7. Furthermore, a lamp starting capacitor C2 is connected between the non-power supply side terminal ``2'' and r4 of each filament of the fluorescent lamp FL.

Next, the operation of the inverter circuit 2 will be explained. In FIG. 1, an AC power supply (not shown) is turned on, and a DC power supply circuit 1
When a DC voltage is generated, a base current is supplied to the transistor Trl via a starting resistor (not shown), and the collector current of the transistor Tri is connected to the parallel resonant circuit of the inductor L1 and the capacitor Ct and the series resonance circuit of the inductor L2 and the capacitor C2. flows through the circuit. Thereby, the transistor Tri is connected to the inductor L2, the feedback winding tl L 2f, the capacitor C3 and the inductor L3
positive feedback from the collector to the base via L
L, L2. Oscillation starts due to resonance of the collector circuit consisting of C1 and C2.

In FIG. 1, capacitor C3 and inductor L3
is for reducing the switching loss of the transistor Tri by drawing out the base current when the transistor Tri is turned off. Variable resistance VR is transistor T
This is a capacitor reset resistor that discharges the charge charged in the capacitor when ri is on when this transistor Trl is off.

This inverter circuit 2 can vary the oscillation frequency of the inverter circuit 2 by varying the reset resistor VR. That is, referring to FIG. 2, during the on period Ton of the transistor Tri, the transistor Tr
The base current flows through capacitor C3, and the feedback winding L2f' side of capacitor C3 is +, and the transistor T
The base side of ri is charged in the negative direction. The charge of this capacitor C3 is transferred from the capacitor C3 to the feedback winding L2f during the next off period Tof'f' of the transistor Tri.
', is discharged via a path returning to capacitor C3 via variable resistor VR and inductor L3.

When the resistance value of variable resistor VR is increased, capacitor C3
The discharge (reset) time constant becomes longer.

Here, the off-period Toff' of the transistor Tri is determined by the resonance system connected to the collector of the transistor Trl, and is therefore substantially constant. Therefore, the amount of charge discharged during the off period Torr of the transistor Trl,
That is, the amount of charge that can be charged during the on period Ton decreases. That is, when the transistor Trl is on, the capacitor C3 is quickly charged when the base current of the transistor Tri flows, and the base current of the transistor Tri quickly decreases, and the transistor Tri is turned off due to the positive feedback described above. As a result, the on period Ton of the transistor Tr1 is shortened and the oscillation frequency is increased.

In this device, the natural frequency of the collector load resonance system of the transistor Tri is set lower than the oscillation frequency of this inverter circuit 2, so if the oscillation frequency of the inverter circuit 2 is increased and moved away from the natural frequency, the lamp current will be reduced. On the other hand, if the oscillation frequency of the inverter circuit 2 is lowered to approach the natural frequency, the lamp current will increase.

Therefore, in this device, the resistance value of the variable resistor VR is set to a predetermined value to turn on the lamp FL at full brightness, and the resistance value of the variable resistor VR is varied or switched to a higher value to control the inverter circuit 2. The lamp FL can be dimmed and lit by increasing the oscillation frequency and decreasing the lamp current.

The dimming switching circuit 3 includes a dimming/all-lighting switch and the like, and is a circuit for setting the lighting state of the lamp FL in a steady state.

The soft start circuit 5 operates for a predetermined period of time immediately after the power is turned on.
This circuit operates the inverter circuit 2 in the same state as during dimming, keeps the voltage applied to the lamp FL lower than the discharge start voltage, and preheats the lamp FL without lighting it.

After fully preheating the lamp FL by the above-mentioned preheating, the full-light starting circuit 2 operates the inverter circuit 2 in the same state as in the full-light mode to apply a voltage sufficiently higher than the discharge starting voltage to the lamp FL, thereby starting the lamp FL. This is the circuit for lighting.

The power supply voltage/temperature compensation circuit 6 controls the resistance value of the variable resistor VR of the inverter circuit 2, that is, the oscillation frequency, compensates for lamp power fluctuations due to power supply voltage fluctuations, and increases the lamp voltage at low temperatures.1. to compensate for starting characteristics and lamp brightness.

The no-load stop circuit 7 is activated when the lamp FL is removed or
This circuit detects a no-load state such as a one-way discharge state and stops the operation of the inverter circuit 2.

The switching improvement circuit 8 is a circuit for improving the switching characteristics of the transistor Tri of the inverter circuit 2.

Since the operations of these circuits 3 to 8 are common to the device shown in FIG. 3, they will be explained with reference to the more detailed circuit diagram shown in FIG.

FIG. 3 shows a circuit configuration of a discharge lamp lighting device according to a second embodiment of the present invention. This device consists of lamps FLI and FL2.
It is designed so that two strokes of and are lit in series.

Also, in place of the variable resistor VR in FIG.
A variable resistance circuit VR consisting of 8 etc. is used. The variable resistor VRI is used to adjust the operating point of the transistor Tr8.

The equivalent resistance value of this transistor Tr8 changes depending on the base current supplied from the power supply voltage/temperature compensation circuit 6. In the device shown in FIG. 3, a zener diode Z is connected to the base of the transistor Tr8 in accordance with the operations of the soft start circuit 5, all-light starting circuit 4, and dimming switching circuit 3.
The lower voltage determined by D's Zener Electric Works (during dimming) and the higher voltage determined by the rectified output of diode D6 (
A current flows based on a voltage that is further compensated for by the power supply voltage and temperature.

Next, the operation of the apparatus shown in FIG. 3 will be explained.

In Fig. 3, the rotary switch SWI serves as both a power switch and a full-light/dimmer switch, and when dimming, it is set to the position shown in the figure, and AC power is supplied to the DC power supply circuit 1 and the dimming switch circuit 3. For example, alternating current power of 100V from AC is supplied. During full light, AC power is supplied only to the DC power supply circuit 2.

When the low-return switch SWl is switched from the power-off state to the cycle-light state, the AC voltage from the AC power supply AC is applied to the protection circuit consisting of fuse F, positive temperature coefficient thermistor PTH, etc., varistor ZNR, balance transformer T1, etc. The signal is supplied to the DC power supply circuit 1 via the noise prevention/surge absorption circuit configured.

The DC power supply circuit 1 rectifies this AC voltage with a full-wave rectifier circuit DB, smoothes it with a capacitor C4, and generates a DC voltage. This DC voltage is applied to the starting resistor R3 of the inverter circuit 2.
The signal is supplied to the base of the switching transistor Trl via the switching transistor Trl. As a result, the inverter circuit 2 starts oscillating, and an alternating current voltage VcL (FIG. 2) is generated at the collector of the transistor Tri. In the autotransformer T2, the winding L1 forms a parallel resonant circuit with the capacitor C6, and the AC voltage Vcl is stepped up and connected via the inductor L2, which is the primary winding of the transformer T3, to the lamp consisting of the capacitor c2, lamps FLI and FL2. Apply to the circuit.

Here, since the lamps FLI and FL2 are not yet lit and are in an open state, the Q of the resonance system connected to the collector of this transistor Tri is high.

Therefore, a larger current flows through the paths of the inductors LL and L2, the capacitor C2, and the fluorescent lamps Fl and F2 than when the lights are turned on due to the resonance of the inductor L2 and capacitor 02, thereby preheating the fluorescent lamps Fl and F2. . At this time, a higher voltage is generated at both ends of the capacitor C2, and therefore at both ends of the series circuit of the fluorescent lamps F1 and F2, than when the lamps are turned on due to the resonance, and this voltage is caused by the discharge of the fluorescent lamps Fl and F2 during cooling. If the voltage is higher than the starting voltage, the fluorescent lamps Fl and F2 will not be preheated after the power is turned on (they will turn on immediately (cold start)).In order to prevent such a cold start, a soft start circuit 5, which will be described later, is provided. be.

Further, the AC voltage induced in the secondary winding of the transformer T3 is rectified and smoothed by the diode D6 and the capacitor C17, and is supplied to the circuits 3 to 7.

In the soft start circuit 5, as explained below with reference to the time chart of FIG. 4, when the power is turned on, the terminal voltage of the capacitor C13 of the all-optical start circuit 4 is zero and the transistor Tr5 is turned off. Transistor Tr
6 is on. Therefore, from this soft start circuit 5, the same voltage as during dimming, which is the zener voltage of the zener diode ZD, is applied via the power supply voltage/temperature compensation circuit 7 to the base of the transistor Tr8 of the variable resistance circuit VR. As a result, the equivalent resistance of the transistor Tr8 becomes the same higher resistance value as during dimming, and the oscillation frequency of the inverter circuit 2 is higher than that during all-optical mode operation, resulting in a current flowing through the resonant circuit and a voltage generated across the capacitor C2. operates in a lower dimming mode than when operating in full light mode.

These currents and voltages in the dimming mode can be set by selecting the value of the capacitor C2 with almost no effect on the lighting characteristics. Here, the voltage generated across the capacitor C2 when the lamps Fl and F2 are off is lower than the voltage that starts discharging the lamps Fl and F2 when the inverter circuit 2 is operated in the dimming mode, and the inverter circuit 2 is operated in the full-light mode. When the lamp Fl, F2
The voltage is set to be higher than the voltage that starts the discharge.

In the all-optical starting circuit 4, capacitor C13 is connected to resistor R9.
is charged via. After the power is turned on, the terminal voltage of the capacitor C13 rises, and this terminal voltage is transferred to the resistor R12.
When the transistor Tr5 is turned on by the voltage divided between Instead, the inverter circuit 2 becomes the all-optical mode. This causes the lamp Fl.

A voltage higher than the discharge starting voltage is applied to F2, and lamps Fl and F2 start discharging and turn on. After lighting, the lamps Fl and F2 connected in parallel to the starting capacitor C2
Since the impedance becomes low, the Q of the load resonance system decreases, and the current of the lamps Fl and F2 is limited by the inductor L2, so that the lamps are lit stably.

In the dimming switching circuit 3, an alternating current voltage input through the low-return switch SWI set to the dimming state is rectified and smoothed by a diode D1 and a capacitor CI2, and then supplied to the base of a transistor Tr2. As a result, the transistor Tr2 is turned on and the transistor Tr3 is turned off.

In this state, in the all-optical starting circuit 4, the capacitor C
H is further charged through the resistor R9 and its terminal voltage rises. When this terminal voltage is divided by the resistors RIO and R11 and the transistor Tr4 is turned on (time t2 in FIG. 4), the transistor Tr5 is turned on. The transistor Tr6 of the soft start circuit 5 is turned on, and the base current of the transistor Tr8 of the variable resistance circuit VR is switched to the smaller one, so that the inverter circuit 2 enters the dimming mode. As a result, the lamps Fl and F2 are lit in a dimmed state from now on.

On the other hand, when the low-return switch SW1 is set to the full-light lighting position, no AC voltage is supplied to the dimming switching circuit 3, and the transistor Tr2 is turned off. Therefore, transistor Tr3 is on, transistor Tr4 is off,
The transistor Tr5 is turned on and the transistor Tr8 is turned off, and the larger current flows through the base of the transistor Tr8 of the variable resistance circuit VR, and the equivalent resistance value of the transistor Tr8 becomes the lower one, so the inverter circuit 2 enters the all-optical mode. . As a result, the lamps Fl and F2 are fully lit.

In FIG. 4, the solid line shows the operation of each part when the rotary switch SWI is set to the dimming state, and the broken line shows the operation of each part when the rotary switch SWI is set to the full light state.

As can be seen from the above, in this device, the capacitor C13 and the resistor R9 are connected to the soft start circuit 5.
It also serves as a timer circuit for both the full-light lighting circuit 4 and the full-light lighting circuit 4.

In the power supply voltage/temperature compensation circuit 6, a voltage obtained by dividing the DC power supply voltage by a resistor R1 and a thermistor ER2 is applied to the base of the transistor Tr7. Therefore, when the power supply voltage increases, the base voltage of the transistor Tr7 increases, the collector current of the transistor Tr7, that is, the base current of the transistor Tr8 decreases, the equivalent resistance value of the transistor Tr8 increases, and the oscillation frequency of the inverter circuit 2 increases. Rise and power the lamp current! reduce on the other hand,
When the power supply voltage decreases, the lamp current increases, contrary to the above. Thereby, the lamp current can be stabilized against fluctuations in the power supply voltage.

Also, as the temperature decreases, thermistors ERI and ER
2 resistance value decreases. Then, the emitter voltage of the transistor Tr7 increases due to the decrease in the resistance value of the thermistor ERI, and the base voltage of the transistor Tr7 decreases due to the decrease in the resistance value of the thermistor ER2. Therefore, the collector current of the transistor Tr7, that is, the base current of the transistor Tr8 increases, the equivalent resistance value of the transistor Tr8 decreases, the oscillation frequency of the inverter 1 path 2 decreases, and the lamp voltage at the time of starting and the lamp current at the time of lighting. increases. Thereby, starting performance at low temperatures and light output at low temperature lighting can be ensured.

In the device shown in FIG. 3, when the lamps Fl and F2 are off, that is, when there is no load, a resonant current due to the inductor L2, capacitor C2, etc. flows through the transistor Trl. Since this resonant current is larger than when the lamp is lit, if this state continues, stress will accumulate in the transistor Tri, or in the worst case, the transistor Tri will undergo thermal runaway and be destroyed. The no-load stop circuit 7 is designed to prevent this.

When there is no load, a larger current flows through the inductor L2 than when there is a load. Therefore, the voltage induced in the secondary winding L2s of the transformer T3 is also larger when there is no load. In the no-load stop circuit 7, when there is no load, the rectified output of the diode D6 increases, and when this state continues for a predetermined period of time, the capacitor CL4 is charged via resistors R17, R18, etc., and its terminal voltage becomes - rise Then, when this terminal voltage becomes higher than the on-voltage of constant voltage element SB5, SB5 is turned on. Due to the stiffness, the cyrisk SCR is turned on, the transistor Tr9 is turned on, the transistor Tri is turned off, and the inverter circuit 2 stops oscillating. This stop state continues until the power is turned off and then turned on again.

FIG. 5 shows a circuit configuration of a discharge lamp lighting device according to a third embodiment of the present invention. The device shown in the figure is an IC version of the dimming switching circuit 3, full-light lighting circuit 4, soft start circuit 5, and no-load stop circuit 7 of the device shown in FIG. 3, except for the time constant circuit portion. In the device shown in Fig. 5, the soft start time constant and the full light lighting time constant are set separately:
I'm being ignored.

FIG. 6 shows a circuit configuration of a discharge lamp lighting device according to a fourth embodiment of the present invention. The device shown in FIG. 3 is different from the device shown in FIG. 3 in that only the temperature compensation circuit portion of the circuits 3 to 8 for controlling the inverter output is left and the circuit configuration of this portion is modified.

In the device shown in FIG. 6, the resistance value of the thermistor TH increases when the temperature decreases. Then, the base voltage of the transistor Tr8 increases, the base current of the transistor Tr8 increases, and the equivalent resistance value decreases.

As a result, in the inverter circuit 2, the on period of the transistor Trl becomes longer, the oscillation frequency decreases, and the output increases. As a result, according to the device shown in FIG. 6, the lamp FL can be started well even at low temperatures and can be lit with the same brightness as at room temperature.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of the inverter circuit in FIG. 1, and FIG. 3 is a circuit diagram of a discharge lamp lighting device according to another embodiment of the present invention. 4 is a timing chart for explaining the operation of each part of the device in FIG. 3, and FIGS. 5 and 6 are a circuit diagram of a discharge lamp lighting device according to still another embodiment of the present invention. FIG. 2 is a circuit diagram of a light lighting device. 1: DC power supply circuit, 2: Inverter circuit, 3: Dimming switching circuit, 4: Full lighting circuit, 5: Soft start circuit, 6: Power supply voltage/temperature compensation circuit, T rl Niswitching transistor, T r8 :
Transistor as a variable resistance element.

Claims (1)

[Claims] 1. In a power conversion device equipped with an inverter that includes a switching element and converts power output from a DC power source into AC power, the ambient temperature of the power conversion device or the load is detected and the detected value is A power conversion device comprising a control circuit that varies the on/off duty and/or frequency of the switching element accordingly. 2. The power conversion device according to claim 1, wherein a reactance element is connected in parallel and/or in series to the output terminal of the inverter. 3. The power conversion device according to claim 1 or 2, wherein the inverter is a single transistor transistor inverter. 4. The inverter is a self-commutated inverter that positively feeds back the output of the switching transistor to the base via a capacitor, and the control circuit converts the charge accumulated in the capacitor by the base current during the ON period of the switching transistor into the switching transistor. The power conversion device according to claim 3, wherein the power conversion device is configured to vary a discharge time constant when discharging during an off period of the transistor. 5. The power conversion device according to any one of claims 1 to 4, which is connected with a discharge lamp as a load and used as a discharge lamp lighting device.