JPS6324590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching regulator type power supply device for a television receiver.
This is intended to prevent the smoothing capacitor from being destroyed when the ground terminal of the primary winding of the converter transformer is disconnected.

Embodiments of the present invention will be described below in connection with a conventional device. The figure shows a power supply device in one embodiment of the present invention.

As shown in the figure, a horizontal component taken out from a flyback transformer is applied to an oscillating section 2 through a capacitor 1, and a rectangular wave signal synchronized with the horizontal component is generated from this oscillating section 2. This rectangular wave signal is amplified by the output section 3 and supplied to the primary winding of the converter transformer 4. The output of the secondary winding of the converter transformer 4 is rectified and smoothed by a rectifying and smoothing circuit comprising a diode 5 and a capacitor 6 to obtain a DC voltage. Fluctuations in the load connected to the rectifying and smoothing circuit are detected from the intermediate tap of the primary winding of the converter transformer 4, and the detected signal is negatively fed back to the transmitter to keep the voltage applied to the load constant. For the above detection, the intermediate tap of the primary winding of the converter transformer 4 is grounded via a resistor, and the signal obtained at this resistor is rectified and smoothed to form a DC voltage and is applied to the oscillation section. On the other hand, although not shown, there is a system that detects the high voltage applied to the cathode ray tube, and if this detected voltage becomes abnormally large, the operation of the horizontal oscillation circuit is stopped to prevent X-rays from being emitted from the cathode ray tube. A protection circuit is provided to prevent The above configuration is a conventional power supply device.

Now, if the ground side of the primary winding of the converter transformer 4 is disconnected, since the intermediate tap of the converter transformer 4 is grounded via a resistor,
Since the signal is boosted and transmitted from the winding between AC in the figure to the secondary side, the voltage that is rectified and smoothed becomes abnormally large. As a result, the capacitor 6 exceeds its withstand voltage and explodes.

The present invention prevents this destruction of the capacitor from occurring. As shown in the figure, the input terminal of the oscillator 2 is connected to the base of a transistor 9 via a diode 7 and grounded via a capacitor 8. The emitter of this transistor 9 is grounded, and the collector of the transistor 9 is connected to a DC power supply terminal 12 via the base of a transistor 10 and a resistor 11. The emitter of this transistor 10 is grounded, and the collector is a resistor 13.
It is connected to the connection point between the oscillation section 2 and the output section 3 via.

If the ground side of the primary winding of the converter transformer is disconnected, the voltage across the capacitor 6 will rise abnormally, and as a result, the high voltage applied to the cathode ray tube will also rise abnormally, so the protection circuit will operate and the operation of the horizontal oscillation circuit will stop. . Then, since there is no pulse in the flyback transformer, there is no horizontal component applied to the oscillator 2. Then, the base potential of transistor 9 becomes 0, and transistor 9 is cut off. As a result, the transistor 10 becomes conductive and there is no output from the output section 3. Therefore capacitor 6
The output voltage of the capacitor 6 also disappears, and the capacitor 6 is not destroyed.

As described above, according to the present invention, even if the ground side of the primary winding of the converter transformer is disconnected, the input to the converter transformer is automatically cut off, so that the smoothing capacitor connected to the converter transformer will not be destroyed. be.

[Brief explanation of drawings]

The figure is a circuit diagram of a power supply device according to an embodiment of the present invention. 1... Oscillation section, 3... Output section, 4... Converter transformer, 5... Rectifier diode, 6... Smoothing capacitor, 7... Diode, 8... Capacitor, 9, 10... Transistor.

Claims (1)

[Claims] 1. An oscillation section that generates a rectangular wave in synchronization with the horizontal component, an output section that amplifies the output of this oscillation section and supplies an input signal to the primary winding of the converter transformer, and an output of the secondary winding of this converter transformer. a rectifying and smoothing circuit that rectifies and smoothes the voltage, a protection circuit that detects the high voltage applied to the cathode ray tube and stops the operation of the horizontal oscillation circuit when the detected voltage becomes abnormally high, and the primary winding of the converter transformer mentioned above. The structure is configured such that fluctuations in the load connected to the rectifying and smoothing circuit are detected from an intermediate tap of the oscillator, and the oscillating section is controlled by the detected voltage to supply a constant voltage regardless of the fluctuations in the load. A power supply device comprising a circuit that detects the presence or absence of a horizontal component supplied to the oscillating section and controls the output of the oscillating section so that it is not supplied to the converter transformer when the horizontal component disappears.