JPS635992B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching regulator type power supply device, in which an error voltage detection circuit that operates when an AC power source is used is used for detecting a stabilized power supply circuit when operating with an external DC power source. The present invention provides a power supply device that can be used in combination as a circuit.

FIG. 1 shows a conventional switching regulator type power supply device. In the figure, 1 is an AC power input terminal, 2 is a rectifier circuit, 3 is a smoothing capacitor, 4 is a power switch, 5 is an output transistor that performs a switching operation, 6 is an output transformer,
7, 8, 9, 10, 11, and 12 are diodes, transistors, resistors, and capacitors that constitute a starter circuit, and the diode 7 is inserted in series between the base of the output transistor 5 and the drive transformer 13. Immediately after the power switch 4 is closed, it is reverse biased and is cut off. The transistor 8 has its collector and emitter connected to both ends of the diode 7, and the power switch 4
When capacitor 12 is charged after closing and the voltage across it reaches a certain value, it becomes conductive and short-circuits diode 7. 14 and 15 are output transformers 6
A diode and a capacitor rectify and smooth the AC voltage obtained in the secondary winding of
It is connected to resistance groups 18, 19, and 20 for detecting fluctuations. 21 is a comparison transistor, the horizontal pulse (sawtooth wave) from the television receiver serving as a load is applied to the base as a trigger, and +B
Its conduction period is controlled according to voltage fluctuations.
Reference numeral 22 denotes a drive transistor, whose output is applied to the base of the output transistor 5 via the drive transformer 13, and the conduction period of the output transistor 5 is controlled to stabilize the output voltage.

23, 24, 25, 26, and 27 are transistors, resistors, Zener diodes, diodes, and capacitors that constitute the APF circuit (active power filter circuit) that operates when using a DC power supply.
8 is a switch interlocked with the power switch 4;
Reference numeral 9 denotes a DC power input terminal, which constitutes a switch circuit with a socket structure.

In the above configuration, the operation when using an AC power source will be explained first. When the power switches 4 and 28 are closed, a DC voltage is generated across the capacitor 3,
The output transistor 5 performs an oscillating operation using this DC voltage, a starting pulse from the third winding 6a of the output transformer 6, and the functions of the resistor 30 and capacitor 31. At this time, the transistor 8 is in a non-conducting state and the diode 7 is reverse biased and cut off, so the base of the transistor 5 is disconnected from the drive transformer 13, so that the transistor 5 performs the switching operation reliably. . This output appears on the secondary side of the output transformer 6, is rectified and smoothed by a diode 14 and a capacitor 15, becomes a +B voltage, and is supplied to a load (not shown).

Note that once the output transistor 5 starts operating, the transistor 8 becomes conductive by charging the capacitor 12, shorting both ends of the diode 7, and coupling the base of the output transistor 5 and the drive transformer 13. On the other hand, the +B voltage is divided by resistance groups 18, 19, and 20, and its fluctuation is detected by transistor 16. This fluctuation is fed back to the base of the output transistor 5 via the transistors 21, 22 and the drive transformer 13, and controls the conduction period of the output transistor 5 which is oscillating in synchronization with the horizontal frequency, thereby stabilizing the output voltage. It's getting older.

In this state, when an external DC power source is connected to the input terminal 29, the DC voltage from this DC power source is higher than the +B voltage, so the DC voltage from the external DC power source is applied to the load via the APF circuit instead of the voltage based on the AC power source. is supplied to Of course, the APF circuit does not operate during AC power supply operation.

In this way, according to this configuration, when an AC power source is used, the output voltage can be stabilized and supplied to the load, and when a DC power source is used, the DC voltage from this DC power source is used in the APF circuit instead of the AC power source. can be supplied to the load as a +B voltage through the +B voltage. However, in this circuit, dedicated circuits must be provided separately for when an AC power source is used and when a DC power source is used.

In view of the above points, the present invention attempts to perform AVR control instead of APF control by using an error voltage detection circuit that is a part of an AC power supply circuit when using a DC power supply. An example of this will be described below with reference to FIG. In FIG. 2, illustrations of the AC power supply rectifying and smoothing circuit, starter circuit, etc. are omitted, and the same components as in FIG. 1 are given the same numbers.

In FIG. 2, a control transistor 33 having a Darlington connection configuration is inserted in series between the +B voltage line and one end of the switch 28, and the base of the control transistor 33 is connected to the DC power supply with the polarity reversed. It is connected to the collector output terminal of the error detection transistor 16 via a protection diode 34, and the conductivity of the control transistor 33 is controlled by the collector output voltage according to fluctuations in the output voltage of this transistor 16, and the output voltage is We are trying to stabilize the situation. Here, resistance 35
is a bias resistor, 36 is a load resistor, and 37 is a protection diode when the DC power supply is connected with the polarity reversed, similar to the diode 34. The B voltage is supplied from the connection point between the resistor 36 and the diode 37.

In this way, according to this configuration, the transistor 16,
By configuring the circuit consisting of the Zener diode 17 to operate as an error voltage detection circuit when operating the DC power supply and perform AVR operation together with the control transistor 33, it is possible to eliminate the need to provide a new detection circuit during the operation of the DC power supply. AVR control can be performed.

As described above, according to the present invention, an error voltage detection circuit that does not work when an AC power supply is operated is operated as a detection circuit of a stabilized power supply circuit when a DC power supply is operated, thereby newly providing a detection circuit when a DC power supply is operated. The power supply stabilization operation can be performed without any trouble.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a power supply device in a conventional example, and FIG. 2 is a circuit diagram of a power supply device in an embodiment of the present invention. 2... Rectifier circuit, 3, 15... Smoothing capacitor, 4, 28... Power switch, 5... Output transistor, 6... Output transformer, 7... Diode constituting the starter circuit, 8... Starter circuit 13... Drive transformer, 14... Rectifier diode, 16, 1
7...Transistor constituting the reference voltage generation circuit, constant voltage element, 21...Comparison transistor, 2
2... Drive transistor, 29... DC power input terminal, 33... Control transistor.

Claims (1)

[Claims] 1 This device is equipped with an output transistor that performs a switching operation, a means for rectifying and smoothing the output of the output transistor by adding it to the primary side of the output transformer and taking it out from the secondary side, and a transistor that detects fluctuations in the rectified and smoothed output voltage. A means for stabilizing the output voltage by controlling the conduction period of the output transistor using the detection output, an input terminal of an external DC power supply, and a means inserted between one end of this input terminal and the output voltage line to operate when the DC power supply is used. and a control transistor for detecting fluctuations in output voltage, and an output end of the output voltage fluctuation detection transistor is connected to a base of the control transistor, thereby stabilizing the output voltage when using an external DC power supply. .