JPH0149236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a power supply circuit for a dual-power type television receiver that can be connected to either an AC power source or a DC power source.

Conventional configurations and their problems Television receivers used in areas where AC power is not available or for leisure use require two types of power supply circuits: AC and DC. FIG. 1 shows an example of a power supply circuit of such a conventional AC/DC receiver. In the figure, 1 is an AC power supply, 2 is a DC power supply such as a battery, and the AC power supply 1 is connected to the P ₁ and P ₂ terminals of one connector 3 of a pair of connectors 3 and 4.
The DC power supply 2 is connected to the P ₃ and P ₄ terminals of the connector 3. When using an AC power supply, the AC power from the S ₁ and S ₂ terminals of the connector 4 connected to the connector 3 is rectified by a rectifier circuit 5, and further smoothed by a smoothing circuit 6, and the smoothed DC is sent to a switching transformer. ₈ and is further connected to the switching transistor 12. The windings N ₃ and N ₄ provided in the switching transformer 8, the capacitor 9, the fixed resistor 10, the voltage stabilizing circuit 11, and the fixed resistor 7 constitute a well-known self-excited switching power supply circuit, which stabilizes the switching transformer 8. The resulting intermittent current flows from the _N2 winding of the switching transformer 8 to the diode 13.
It is rectified via a capacitor 14 and applied to the _N5 winding of a flyback transformer (hereinafter referred to as FBT) 16, and the horizontal deflection circuit 15 operates. Since this operation is also well known, the explanation thereof will be omitted. A trigger pulse is applied from the _N8 winding of this FBT 16 to the base of the switching transistor 12 via the fixed resistor 24 and diode 23, and the above-mentioned switching power supply circuit is turned on and off in synchronization with the horizontal deflection frequency. AC frequency interference to the receiver screen can be removed.

When using a DC power supply, P ₃ of connector 3,
From the P ₄ terminal to the S ₃ and S ₄ terminals of connector 4,
A DC power supply 2 is added to a voltage stabilizing circuit consisting of an AVR output transistor 20, a fixed resistor 21, a Zener diode 22, etc., and a stabilized DC voltage is output from the emitter of the AVR output transistor 20.
Added to _N5 winding of FBT16, horizontal deflection circuit 1
5 is activated, and the television receiver is activated.

In the circuit described above, the trigger pulse from the _N8 winding of FBT 16 is necessary when the receiver operates on AC power, but is not required when the receiver operates on DC power. However, in the conventional circuit, even when operating on a DC power supply, a trigger pulse is applied to the switching transistor 12 from the _N8 winding of the FBT. Therefore, there is a drawback that power is wasted in the _N8 winding, fixed resistor 24, diode 23, switching transistor 12, etc.

Purpose of the Invention As described above, the present invention uses a switching method using a flyback pulse as a trigger pulse to stabilize the AC power supply, and uses a separate stabilization circuit for the DC power supply in the power supply circuit of an AC/DC receiver. The purpose is to eliminate wasteful power consumption when using a DC power source.

Structure of the Invention The present invention supplies a trigger pulse from an FBT via a switch to a switching transistor in a power supply circuit using a switching method, and controls the switch to close when AC power is used and open when DC power is used. Accordingly, the trigger pulse is not supplied to the switching transistor of the switching circuit when a DC power source is used.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 shows a circuit of one embodiment of the present invention. In the figure, the same parts as in FIG. 1 are given the same reference numerals. The AC power supply 1 is connected to the P ₁ and P ₂ terminals of the connector 3, and from the S ₁ and S ₂ terminals of the connector 4 via the rectifier circuit 5 and the smoothing circuit 6, is connected to the switching transformer 8.
is connected to the _N1 winding of , and further connected to the switching transistor 12 . The switching transformer 8 is stabilized by a self-excited switching power supply circuit consisting of N ₃ and N ₄ windings, a capacitor 9, a fixed resistor 10, a voltage stabilizing circuit 11, and a fixed resistor 7. Transformer 8 N ₂
The current from the winding is converted into direct current by a diode 13 and a capacitor 14, and connected to the _N5 winding of the FBT 16 to operate the horizontal deflection circuit 15. Further, the DC power supply 2 is connected to the P ₃ and P ₄ terminals of the connector ₃ , and _the AVR output transistor 20,
It is connected to the _N5 winding of the FBT 16 via a voltage stabilizing circuit consisting of a resistor 21 and a Zener diode 22. The above is the same as the circuit shown in FIG.

In the present invention, the _N8 winding of the FBT 16 is connected to the collectors of two Darlington-connected transistors Q ₁ and Q _{2 configuring the switch circuit 25, and the emitter of the transistor Q 2 is} connected to the switching circuit of the self-excited switching power supply circuit. It is connected to the base of the transistor 12, and the output voltage of the AC power rectifier circuit 5 is applied to the base of the transistor _Q1 via a fixed resistor _R1 .

In the above configuration, when the receiver operates on an AC power supply, a DC output is output to the rectifier circuit 5, so that voltage is applied to the base of the transistor _Q1 via the fixed resistor R1, and the transistor _{Q1 is} Then, the emitter output of Q ₁ is applied to the base of transistor Q ₂ , Q ₂ is also turned on, and a trigger pulse is applied from the _N8 winding of FBT 16 to the base of switching transistor 12 via transistor Q ₂ . is added to normal operation.

Also, when operating with a DC power supply, the rectifier circuit 5 has no output voltage, so the base voltage of the transistor _Q1 is 0, so _Q1 is off, _Q2 is also off, and the _N8 winding of the FBT16 is turned off. No trigger pulse from is applied to the base of switching transistor 12. Therefore, when the receiver operates on DC power, the power of the storage battery is not wasted due to the trigger pulse.

In addition, in Fig. 2, 17 is a cathode ray tube,
Also, diode 18, capacitor 19, winding N ₇
The voltage _B2 obtained at is the power supply for other circuits of the receiver.

Effects of the Invention According to the present invention, by eliminating the trigger pulse required when operating on an AC power source when the receiver operates on a DC power source, unnecessary power consumption can be eliminated, especially in overseas areas where there is no AC power source. The present invention can be used in a television receiver used in a TV or a television receiver for leisure use to reduce battery power consumption and allow the television receiver to operate for a long time.

[Brief explanation of drawings]

FIG. 1 shows a power supply circuit of a conventional AC/DC television receiver, and FIG. 2 shows a power supply circuit of an embodiment of the present invention. 1... AC power supply, 2... DC power supply, 3, 4...
Connector, 5... Rectifier circuit, 8... Switching transformer, 11... Voltage stabilization circuit, 12... Switching transistor, 15... Horizontal deflection circuit, 16... Flyback transformer, 17... Braun tube, 20 ...AVR output transistor, 2
2... Zener diode, 25... switch circuit.

Claims (1)

[Claims] 1. A first circuit that rectifies the alternating current, uses a flyback pulse as a trigger pulse to turn on and off the direct current using a switching transistor, stabilizes the voltage, and supplies it to the flyback transformer via the rectifier circuit. , a second stabilized DC power supply voltage and supplied to the flyback transformer;
In a television receiver configured to operate on either AC or DC power, the circuit includes a circuit that applies a trigger pulse from the flyback transformer to the base of the switching transistor. A switch is provided that automatically closes when connected to the AC power source under the control of a DC voltage obtained by rectifying the AC power source, and automatically opens due to the absence of the DC voltage when connected to the DC power source. A power supply circuit for a television receiver that automatically cuts off a trigger pulse applied to a switching transistor when the machine operates on a DC power supply.