JPS5820557B2 - inverter warmer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter circuit, and its purpose is to provide an inverter circuit that can control light output and reduce power consumption when used in a lighting circuit. It is on offer.

Figure 7 shows an example of a general inverter circuit driven by a DC input voltage VDc, in which R1 is a starting resistance, R2 is a base resistance, C1 is a capacitor, and LB is an oscillation transformer O.
The base winding of T, Lc is the collector winding of the oscillation transformer OT, L is the load, and Trl is the oscillation transistor.

When the input voltage VDO increases in this circuit, the output and loss of the inverter circuit also increase, and the efficiency decreases, so the oscillation transformer OT and the inverter transistor Tr1
This has the drawback that heat generation increases and circuit reliability decreases, and if overvoltage is applied, there is a risk of thermal runaway in these inverter transistor Tr1 and oscillation transformer OT. It was difficult to use.

Furthermore, if a constant voltage device is used in the circuit on the input power supply side, it becomes a power circuit control, and it is necessary to use high-power components for this constant voltage device, which increases the cost of the device and generates heat in each of the above components. Even if countermeasures were taken, there was still a drawback that the equipment would become expensive.

Therefore, conventionally, as shown in FIG. 8, a transistor Tr 2 is provided in the starting circuit of the transistor inverter A, and the voltage on the load side is returned directly from the slider of the variable resistor VR and applied to the base of the transistor Tr 2 , and the output voltage is A circuit is provided that controls the base current according to the current.

However, in such a conventional example, since the output is looped back, there is a problem that the response is delayed if an overvoltage is instantaneously applied between the terminals of the input voltage VDO, and the transistor Tr2 always keeps the active region Therefore, if the voltage fluctuation is large, the transistor T
r2 becomes saturated, which has the disadvantage of making it impossible to supply power to the load, and furthermore, the oscillation transformer O
Since T is a single-turn transformer, there is a risk of a short-circuit in the input circuit due to a short circuit at one point, creating a danger.Also, since the load side voltage is high, there is a risk of electric shock when used in a lighting circuit. In addition to this problem, since the base current is directly controlled, starting is difficult, especially at low temperatures.

The present invention has been provided in view of the above points, and one embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention, in which a DC input voltage ■Dc is detected by an input voltage detection circuit C, and an output is generated when a voltage exceeding a certain level is detected, and FIG. 7 shows a conventional example. Control circuit B for variable control of starting resistance provided in the starting circuit of transistor inverter A having the same configuration as
is controlled by the output of the input voltage detection circuit C.

FIG. 2 shows a specific circuit example corresponding to the block diagram in FIG. 1, in which a ballast 1 and a commercial lighting device 4 consisting of a fluorescent lamp and a glow discharge tube 3 are connected to both ends of a commercial power supply AC. The output terminal of the transistor inverter A is connected to the fluorescent lamp serving as the light source load of the commercial lighting device 4 via the NC terminal of the switching contact of the power failure detection relay Ry to provide an emergency lighting device.

The transistor inverter A is designed to oscillate the DC power supply DC by turning on the contact r of the relay Ry during a power outage of the commercial power supply AC. The input voltage detection circuit B is composed of the transistor Tr3 and the Zener diode Dz, and the transistor Tr2 has a collector-emitter circuit inserted in series with the starting circuit of the transistor inverter A, and the transistor Tr2
A control circuit B for variable control of the starting resistance is constituted by a resistor R4 connected between the collector and the emitter and a resistor R5 connected between the collector and base.

However, in the above embodiment, when commercial power AC is supplied, relay Ry operates to connect the fluorescent lamp to the ballast 1 side and connect the glow discharge tube 3 in parallel to the fluorescent lamp, so that the commercial The lighting device 4 operates and lights up the fluorescent lamp 2.

Next, when the commercial power supply AC is out of power, the operation of the commercial lighting device 4 is stopped, the fluorescent lamp is connected to the transistor inverter A side, and the DC power supply DC is connected to the transistor inverter A by closing the contact r of the relay Ry. ,
Transistor inverter A operates, and the fluorescent lamp is lit with high frequency alternating current from transistor inverter A instead of commercial alternating current.

At this time, the DC input voltage ■Dc input to the transistor inverter A is a constant voltage (for example, 13
0V) or more, R″VD0>R6+R7 Vz+VBB (Vz: Zener voltage, VBE: Tr
If the constants of each part are set so that the following relationship is established, the transistor Tr of the input voltage detection circuit C
3 is turned on, and transistor Tr2 of control circuit B is turned on.
is off.

Therefore, the starting resistance of the starting circuit of the transistor inverter A is increased by inserting the resistor R4 of the control circuit B in series, and the base current of the transistor Trl of the transistor inverter A is controlled.

Therefore, the input power of transistor inverter A is kept low as shown by ■ in Figure 3, and it is possible to obtain a proper output and protect transistor inverter A by preventing thermal runaway of transistor Trl due to excessive input. .

Next, the voltage of the DC power supply DC gradually decreases, the input voltage detection becomes a constant voltage, and R7VDO~ -= v7. +vBE R6+R7, the transistor Tr3 of the input voltage detection circuit C
begins to turn off, the transistor Tr2 of the control circuit B begins to shift to the off state, the impedance at both ends of the resistor R4 of the control circuit B becomes low, and the base current of the transistor inverter A begins to increase.

Therefore, the input/output power of the transistor inverter A does not show a large change and is kept substantially constant, as shown by .circle. in FIG. 3.

At this time, the switching of the transistor Tr2 is not sudden but gradual, so there is only one stable point, there is no unstable region, and the fluorescent lamp does not flicker.

Furthermore, when the input voltage of transistor inverter A becomes even lower, the relationship becomes R7VDO -<Vz + VBE R6+R7, and transistor T of input voltage detection circuit
r3 is turned off, and the transistor Tr of control circuit B
2 turns on.

Therefore, the resistor R4 of the control circuit B is short-circuited, and the base current of the transistor inverter circuit A increases, thereby preventing a sudden drop in input and output power.

In this embodiment, it is possible to suppress as much as possible a decrease in the light output of the fluorescent lamp due to a voltage drop in the DC power source DC.

Further, in this embodiment, the transistor Tr2 y T
Even if rs is short-circuited or open, power can be supplied to the transistor inverter A, improving the reliability of the emergency lighting system.

Furthermore, since the circuit as described above is used, the oscillation transformer OT of the transistor inverter can be constructed of an isolation transformer, and the power consumption required for control can be reduced.

Incidentally, the broken line in FIG. 3 indicates the conventional example.

FIG. 4 shows a comparison graph between the circuit of the embodiment of the present invention and the conventional circuit, where the solid line indicates the conventional circuit and the broken line indicates the embodiment.

In addition, P1 in the figure. P'1 is input power, P, y is loss, IDC
, I'DC is the input current, lHF1. Iil indicates the lamp current, respectively.

FIG. 5 shows a circuit according to another embodiment of the present invention, including a control circuit B in which a plurality of control transistors Tr2 are connected in parallel, and an input voltage detection circuit C corresponding to the transistor Tr2 of the control circuit B. A plurality of transistors Tr3... are provided in parallel, and control operating voltages are set sequentially, so that any output can be obtained for any input voltage.

Therefore, in this embodiment, not only a more stable output can be obtained, but also the starting current of the transistor inverter A at low voltage input can be increased to improve starting.

Furthermore, the output at low pressure can be increased compared to the conventional method.

In FIG. 6, a plurality of transistors Tr2 of control circuit B are connected in series, and a plurality of transistors Tr3 of input voltage detection circuit C corresponding to transistor Tr2 are also connected in series to obtain the same control operation as in FIG. This is how it was done.

Note that a combination of the above-mentioned parallel and series connections may also be used.

Further, the resistor R1 on the emitter side of the transistor Tr2 may be on the collector side.

Furthermore, the resistor R4 connected in parallel to the transistor Tr2 may be connected in parallel to both ends of the series circuit of the transistor Tr2 and the resistor R1.

In addition to the resistor R4 connected in parallel to the transistor Tr2 and the resistor R1 connected in series, a resistor may be connected in parallel to both ends of the resistor R1 and the resistor R4.

For temperature compensation, one of the resistors R6 and R7 of the input voltage detection circuit C may be configured with a positive characteristic thermistor or a negative characteristic thermistor.

Furthermore, the starting resistors such as the resistors R1t and R4, which control the base current, may be composed of a positive characteristic thermistor or a negative characteristic thermistor for temperature compensation.

The present invention provides a starting circuit for a transistor inverter with a control circuit that varies the magnitude of starting current, and also includes an input voltage detection circuit that detects the input voltage of the transistor inverter. Since the control circuit is controlled by the output of the input voltage detection circuit in the direction of decreasing the starting current and increasing the starting current when the detected voltage is low, the control response is quick and the control range is widened. Therefore, it can also be used for transistor inverters with large input voltage fluctuations.For example, when an overvoltage is input, the input/output power can be kept constant or small by controlling the starting current that tends to rise due to the overvoltage to a smaller value. It has the effect of being able to protect the circuit from the surrounding voltage, and also has the effect of being able to be manufactured compactly and at low cost because of its simple structure.

[Brief explanation of drawings]

Figure 1 is a circuit configuration diagram of an embodiment of the present invention, Figure 2 is a specific circuit diagram corresponding to the above, Figure 3 is an input voltage-input/output power characteristic diagram of the same, and Figure 4 is the same as the above and a conventional example. FIG. 5 is a circuit diagram of another practical side of the present invention, FIG. 6 is a circuit diagram of another embodiment of the present invention, FIG. 7 is a circuit diagram of a conventional example, and FIG. is a circuit diagram of another conventional example, and A
is a transistor inverter, B is a control circuit, and C is an input voltage detection circuit.

Claims (1)

[Claims] 1 The starting circuit of the transistor inverter is provided with a control circuit that varies the magnitude of the starting current, and is also provided with an input voltage detection circuit that detects the input voltage of the transistor inverter, and when the detected voltage of the input voltage detection circuit is high, the starting current is An inverter circuit characterized in that the output of the input voltage detection circuit controls a control circuit in the direction of increasing the starting current when the detected voltage is low.