JPH0320989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a power supply device having a transistor inverter and supplying a high frequency output to a load.

(Background of the Invention) Conventionally, as this type of power supply device, one having the configuration shown in FIG. 1 is known. The device shown in the figure includes a one-stone blocking oscillation type transistor inverter 5 consisting of an AC power supply 1, a rectifier 2, a high frequency blocking film 3, an auxiliary power supply circuit 4, an output transformer 51, an output transistor 52, etc., and a discharge lamp as a load. 6, and furthermore, the inverter 5 or the load 6 connected to this inverter 6 is connected to the AC power source 1.
In order to protect against overload or overvoltage caused by surge voltages generated by the power source, etc., a power surge protection circuit 7 consisting of a thyristor 71, a zener diode 72, etc. is added.

In this device, during operation, when a surge voltage occurs in the AC power supply 1, etc., and a voltage higher than the zener voltage of the zener diode 72 in the protection circuit 7 appears in the input circuit of the inverter 5, the zener diode 72 turns on. The thyristor 71 is turned on when a voltage generated across the resistor 73 by the current flowing through the Zener diode 72 is applied to its gate. As a result, the base and emitter of the output transistor 52 of the inverter 5 are short-circuited and turned off, the inverter 5 stops oscillating, and the inverter 5, load 6, etc. are protected from overload or overvoltage due to this surge voltage.

In addition, as an additional circuit or an additional function in such an inverter, the lamp life is detected from voltage or current distortion due to one-way discharge of the discharge lamp 6, and the output transistor 52 is turned off. This is a safety circuit that prevents damage to the lamp bulb due to abnormal heating and overloading of the inverter 5, and a safety circuit that was previously proposed by the present inventors. A switching element connected between the emitters, such as a transistor 81
The transistor 81 is turned on in each period of the high-frequency output generated by the inverter 5 in each period in which the base current becomes positive even before the collector-emitter voltage of the output transistor 52 crosses zero. A base current control circuit is known that attempts to reduce the switching loss of the output transistor 52 by bypassing the base current of the lever.

However, conventionally, each of these additional circuits has been considered independently and separately, and adding these circuits to an inverter has the disadvantage that the circuit configuration becomes correspondingly complex.

(Object of the Invention) In view of the above-mentioned problems with the conventional type, an object of the present invention is to improve the circuit efficiency of the inverter and to prevent power surges in a power supply device that uses a transistor inverter to generate high-frequency output.
The object of the present invention is to realize protection against load abnormalities and the like with a simple circuit configuration.

(Structure of the Invention) In order to achieve the above object, the present invention provides a differentiating circuit for differentiating the output voltage of the base feedback winding, and a differentiating circuit for differentiating the output voltage of the base feedback winding in a power supply device including a blocking oscillation type transistor inverter and supplying a high frequency output to a load. an unnecessary drive voltage detection circuit that has a reference circuit that outputs a signal when the output of
The present invention is characterized in that a switching element is provided which operates based on the logical sum output of the outputs generated by the unnecessary drive voltage detection circuit and the abnormality detection circuit, and bypasses the base current of the output transistor of the inverter.

(Description of Examples) Examples of the present invention will be described below with reference to the drawings. Note that parts common or corresponding to those of the conventional example are represented by the same reference numerals.

FIG. 3 shows a circuit configuration of a power supply device according to an embodiment of the present invention. In the figure, 1 is an AC power supply,
A rectifier 2 is connected to this AC power supply 1, and a high-frequency blocking filter 3 is connected between the output terminals a and b of the rectifier 2 to connect the power storage capacitor 41 and charging current limiting inductor 42 of the auxiliary power supply circuit 4 to isolators. A series circuit with a rate diode 43 and a single-stone blocking oscillation type transistor inverter 5 are connected.

The rectifier 2 includes a power surge absorption circuit composed of a full-wave rectifier circuit 21, a short-circuit protection fuse 22, and a bidirectional constant voltage element such as a varistor 23, and has a non-smooth rectified output (pulsating output) from the AC power supply 1. occurs.

The high frequency blocking filter 3 consists of an inductor 31, a capacitor 32, and a balanced transformer 33, and prevents high frequency currents such as the charging current to the capacitor 41 of the auxiliary power circuit 4 and the current supplied to the inverter from flowing into the AC power supply 1, and prevents the noise from flowing into the AC power supply 1. Efforts are being made to reduce voltage. Further, the inductor 31 and the inductor 42 also have the role of limiting the charging current to the capacitor 41 of the auxiliary power supply circuit 4 and regulating the power stored in the capacitor 41.

The inverter 5 includes an output transformer 51, an output transistor 52, a base drive circuit 53, etc., and one end of the primary winding 51p of the output transformer 51 is connected to the positive output terminal a of the rectifier 2 via the filter yoke 31. Connect the other end to the output transistor 5
2 and this primary winding 5.
A resonant capacitor 54 is connected in parallel with 1p, the emitter of the output transistor 52 is connected to the negative output terminal b of the rectifier 2 via a diode 55, and the base winding 51b of the output transformer 51 has one end connected to the output transistor 52. Base drive circuit 53 on the base
The other end is connected to the negative side output terminal b of the rectifier 2. The diode 55 is for protecting the transistor 52 from emitter-base reverse voltage and for supplying just the right amount of base extraction current.

Furthermore, the base of the output transistor 52 of this inverter 5 and the negative side output terminal b of the rectifier 2
A switching element, such as a transistor 9, which is a feature of the present invention, is connected between the two, and the output terminals of the power surge detection circuit 7 and the unnecessary drive voltage detection circuit 8 are connected to the base of the transistor 9.
The collector of the output transistor 52 and the inductor 42 and diode 4 of the auxiliary power supply circuit 4
A discharge lamp 6 is connected to the secondary winding 51s of the output transformer 51 as a load.

Next, the operation of the apparatus configured as above will be described.

Now, when the AC power supply 1 is turned on, a full-wave rectified output is generated from the rectifier 2, and this is given to the inverter 5. As a result, in the inverter 5, the rectified output is passed through the starting resistor 56 to the transistor 5.
2 as the base current, and the transistor 5
2 turns on. Thereafter, the transistor 52 oscillates due to positive feedback between the collector and base, the inductance of the primary winding 51p, and the resonance of the capacitor 54, and each winding 51p, 51s,
A high frequency output is generated at 51b.

In the auxiliary power supply circuit 4, the capacitor 32 is turned on every time the transistor 52 of the inverter 5 is turned on.
On the other hand, a closed circuit is formed via a capacitor 41, an inductor 42, a diode 44, the transistor 52, and a diode 55. It is charged in a predetermined direction. Further, when the rectified output of the rectifier 2 becomes lower than a predetermined voltage every half cycle of the AC power supply 1, that is, the charging voltage of the capacitor 41 in this embodiment, the capacitor 41 is discharged via the diode 43, and this discharge output is transferred to the inverter 5. give to

Since this device does not have a smoothing capacitor in the main rectifier 2, the input power factor is high.Moreover, in the section where the output voltage of the rectifier circuit is lower than a predetermined voltage, DC voltage is supplied from the auxiliary power supply circuit 4 to the inverter 5. It is possible to supply a high frequency output with little ripple to the load without any rest periods.

In addition, in the unnecessary drive voltage detection circuit 8, as _shown in FIG.
Detects the period T in which the voltage exceeds the zener voltage, that is, the period T in which the forward base current I _B is supplied to the output transistor 52 in each cycle of the high-frequency output, and in which the collector-emitter voltage is applied before the zero cross. By turning on transistor 9 using this detection output (I ₈₂ ),
The base current I _B to the output transistor 52 during the period T is bypassed. ( _I9 ). This results in
The output transistor 52 is turned off before the collector-emitter voltage crosses zero, and the switching loss of the output transistor 52 can be reduced compared to the conventional example in which the output transistor 52 is turned on. Note that the diode 91 is for protecting the transistor 9 from base-emitter reverse voltage, similar to the diode for the output transistor 52.

The diode 91 may be omitted by connecting the emitters of the transistor 9 and the output transistor 52 in common as shown in FIG. Further, as shown in FIG. 5, the capacitor 82 is discharged by R without using the reset D84 534,
A circuit configuration without 533 and 535 may be used.

Furthermore, transistor 9, zener diode 72
The resistor 73 and the like constitute a power surge protection circuit similar to that shown in FIG. 1, and operate in the same manner as explained in FIG. That is, when a surge voltage occurs in the AC power supply 1 etc. and a voltage higher than the zener voltage of the zener diode 72 of the surge voltage detection circuit 7 appears in the input circuit of the inverter 5, the transistor 9 switches between the zener diode 72 and the resistor 74.
A base current is supplied through the diode 75 to turn it on. As a result, the output transistor 52 of the inverter 5 is turned off and oscillation is stopped, and the inverter 5 and the load discharge lamp 6 etc. are protected from overload or overvoltage.

In the device shown in FIG. 3, the inverter 5
A winding terminal C is provided on the output transformer base winding 51b, and this terminal C is connected to the base of the transistor 533, and the collector and emitter of this transistor are connected to both ends of the capacitor 531 and the capacitor 82 of the unnecessary drive voltage detection circuit 8, respectively. The connection is made through diodes 534 and 84. As a result, the transistor 533 is turned on when the base winding 51b voltage is negative, and the capacitor 531 is turned on when the base winding 51b is positive.
and 82 are discharged, and these capacitors 531 and 82 are reset. If the capacitors 531 and 82 are forcibly reset by the transistor 533 or the like in this way, problems such as a reduction in the resonance Q, a shift in the operating level, and a delay in the operating timing will occur due to the provision of a discharge resistor in parallel with each capacitor. Therefore, as long as there is no problem in the above-mentioned points, for example, as shown in FIG. By omitting this, it is possible to simplify the circuit configuration and reduce costs.

FIG. 7 shows a circuit configuration of a power supply device according to another embodiment of the present invention. This device is the same as the device shown in FIG. 3 with a lamp life detection circuit 10 added thereto.

Referring to FIG. 7, when the discharge lamp 6 reaches the end of its life and the discharge current shifts to one side, resulting in a so-called one-way discharge state, the induced voltage in the detection winding 51d of the output transformer 51 is on the polarity side where the load current is smaller. Peak value increases. This lamp life detection circuit 10 includes a full-wave rectification circuit 10 that rectifies the induced voltage in the detection winding 51d.
1 and a capacitor 102 that is charged to almost the peak value of the output voltage of this rectifier circuit 101. When the lamp is in a one-way discharge state, that is, at the end of its life, the terminal voltage of the capacitor 102 exceeds the zener voltage of the zener diode 103. When it exceeds this, this zener diode turns on. Therefore, current flows through the resistor 104 and a voltage is generated across it, the thyristor 105 is turned on with the voltage across the resistor 104 applied to its gate, and the transistor 9 is turned on by the voltage across the resistor 104.
02 to thyristor 105 and diode 10
6. A base current is supplied through the resistor 74 to turn it on. As a result, the output transistor 52 is turned off and the inverter 5 stops operating. However, in this case, when the inverter 5 stops operating, the output of the detection winding 51d becomes zero, so the capacitor 102
is not charged. Therefore, the capacitor 102 is
The thyristor 105 and the transistor 9 are discharged through the base and emitter paths of the thyristor 105, the resistor 74, and the transistor 9 in a time determined by the time constant of the capacitor 102, the resistor 74, etc., and the thyristor 105 and the transistor 9 operate with the current supplied from the capacitor 102. is turned off. Therefore, the inverter 5 oscillates again to generate a high frequency output, and the discharge lamp lights up in a one-way discharge state. After that, the capacitor 102
is charged, one-way discharge is detected, thyristor 105 and transistor 9 are turned on, inverter 5 is stopped, and thyristor 10 is discharged by discharging capacitor 102.
5 and transistor 9 are turned off and the inverter 5 is restarted, so in this device, at the end of the discharge lamp's life, the inverter 5 intermittently generates high-frequency output, and the discharge lamp blinks at almost constant intervals. It will be repeated.

Note that the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within the scope of the spirit of the present invention. For example, in the above description, a power supply device using the auxiliary power source 4 including the capacitor 41 and the like has been described, but the present invention can of course be applied even when the auxiliary power source 4 is not provided. Furthermore, in the above-mentioned embodiments, the DC power source is composed of an AC power source and a non-smooth rectifier and generates a non-smooth pulsating output.
A pure DC power source such as a smoothed rectified output or a battery may be used.

(Effects of the Invention) As described above, according to the present invention, various functions are realized by bypassing the base current of the output switching transistor of the inverter, and the bypass switching element is also used for each function. Therefore, (number of added functions - 1) switching elements can be omitted, and the circuit can be simplified and costs can be reduced.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams of a conventional power supply device,
FIG. 3 is a circuit diagram of a power supply device according to one embodiment of the present invention, FIGS. 4 to 6 are partial circuit diagrams showing modifications of the device of FIG. 3, and FIG. 7 is a circuit diagram of a power supply device according to another embodiment of the present invention. A circuit diagram of such a power supply device, and FIG. 8 is a waveform diagram for explaining the operation of the unnecessary drive voltage detection circuit of FIG. 3. 1... AC power supply, 2... Full wave rectifier circuit, 5...
Inverter, 51... Output transformer, 52... Output transistor, 6... Load, 7... Power surge detection circuit, 8... Unnecessary drive voltage detection circuit, 9
...Transistor, 10...Lamp life detection circuit.

Claims (1)

[Claims] 1. A DC power source, an output transformer, and an output transistor that energizes the primary winding of the output transformer, and oscillates by a base current that is positively fed back from the base feedback winding of the output transformer. and a power supply device comprising a transistor inverter that generates a high frequency output from the DC power supply and supplies the high frequency output to a load, comprising: a differentiating circuit that differentiates the output voltage of the base feedback winding; and an output of the differentiating circuit that is equal to or higher than a predetermined value. an unnecessary drive voltage detection circuit having a reference circuit that outputs a signal when an abnormality occurs in the DC power supply, the load, or the inverter; an abnormality detection circuit that generates a signal when an abnormality occurs in the DC power supply, the load, or the inverter; and a switching element that bypasses the base current of the output transistor by operating according to the logical sum output of the signals generated by the respective output transistors. 2. The power supply device according to claim 1, wherein the abnormality detection circuit includes a power surge detection circuit. 3. The power supply device according to claim 1 or 2, wherein the load is a discharge lamp, and the abnormality detection circuit includes a lamp life detection circuit that detects voltage or current distortion due to one-way discharge of the discharge lamp.