JPS5922248B2 - DC stabilized power supply circuit for television receivers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stabilized DC power supply circuit for a television receiver, and more particularly to a stabilized DC power supply circuit for a television receiver that can obtain a predetermined constant voltage output even when connecting DC power supplies with different voltages. It is something.

As the input voltage of the DC stabilized power supply circuit of the television receiver,
When using a DC power source such as a battery, there are various voltages of the DC power source such as 12V, 24V, etc., for example.

When a series-controlled constant voltage power supply using transistors is used for these multiple input voltages, the internal impedance variable range of this transistor will inevitably become wider.
This causes various problems such as extremely low efficiency as a constant voltage power supply. To eliminate this inconvenience, a chopper-type stabilized power supply circuit is used, which has a relatively wide control range and is highly efficient against wide changes in input DC voltage, but this chopper-type power supply circuit has a complicated circuit configuration. Then,
Moreover, it has the disadvantage that it causes significant high-frequency interference to television receivers.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a DC stabilized power supply circuit for a television receiver, which has a simple circuit configuration, does not cause adverse effects such as high frequency interference, and is inexpensive.

A preferred embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2.

FIG. 1 is a block circuit diagram showing one embodiment. A DC power source (not shown) such as a battery is connected between the DC power input terminals 10 and 11, and a predetermined DC voltage (for example, 12V) is connected between the DC power input terminals 10 and 11.
Alternatively, 24V) is applied. A plurality (for example, two) of regulator control units 2 and 3 are connected to the positive input terminal 10 in parallel with each other. The control units 2 and 3 of these two regulators each have different regulated voltage ranges. For example, the control unit 2 operates at an input voltage of around 24 V for high voltage, and the control unit 3 operates for low voltage. For practical purposes, it should be set to operate at an input voltage of around 12V. A selection section 4 is connected to the positive input terminal 10, which detects the applied DC voltage and selectively operates the control sections 2 and 3 of the regulator. That is, this selection section 4 operates the control section 2 of the high voltage regulator when the applied voltage is in the voltage range of around 24V, and operates the control section 3 of the low voltage regulator when the applied voltage is in the voltage range of around 12V. A comparison unit 5 is connected to an output terminal of the control unit 2 . This comparison section 5 detects the output voltage of the control section 2 (this is also the output voltage of the DC power supply circuit of this embodiment), compares it with a reference voltage, and amplifies the error voltage as necessary to control the Return to parts 2 and 3. The control units 2 and 3 perform internal resistance value control according to the amount of feedback. In this way, the control section 2 obtains a constant voltage output (for example, 12V) corresponding to the input voltage of 24V, and the control section 3 obtains a constant voltage output of an output voltage (for example, 6V) corresponding to the input voltage of 12V. By the way, the 12V constant voltage output is used as it is as the output of this DC stabilized power supply circuit, but the 6V constant voltage output is converted to 12V DC by a DC-DC converter.

This DC-DC converter is constructed using a horizontal deflection output circuit of a television receiver. That is, one end 83 of the primary winding of the flyback transformer 8 is connected to the switching section 6 that switches according to the horizontal synchronizing signal, and the output terminal of the control section 2 is connected to the other end 81 of this primary winding. At the same time, the output terminal of the control section 3 is connected to the intermediate terminal 82 of the primary winding via the boost-up diode 7. The voltage ratio between this intermediate terminal 82 and the terminal 81 is 1:2. A more specific example of the configuration of the above circuit will be described with reference to FIG. In FIG. 2, parts that are equivalent to those in FIG. 1 are given the same numbers. First, a case will be described in which a DC power source having an output voltage range of around 12V is connected between the DC power input terminals 10 and 11.

In the selection section 4, the applied voltage is divided by voltage dividing resistors 43 and 44, and this divided voltage is applied to the base of the transistor 41. Further, an input voltage is applied to the base of the transistor 42 via a Zener diode node 45.

The transistor 41 constitutes a differential circuit together with the transistor 42, and the 0N of these transistors 41 and 42
, 0FF operations are opposite to each other. The applied voltage is 12V
When the voltage is close to that, the Zener diode 45 connected to the base of the transistor 42 has not broken down, so the transistor 41 becomes 0N and the transistor 42 becomes 0FF. At this time, the base of the control transistor 21 constituting the control section 2 of the high voltage regulator is connected to the selection section 4.
It is grounded through the transistor 41 and becomes non-conductive. On the other hand, regarding the control transistor 31 constituting the control section 3 of the low voltage regulator, since the transistor 42 of the selection section 4 is 0FF, the power supply current from the input terminal 10 flows to the base of the transistor 31 via the resistor 32. . Therefore, a predetermined control operation of the low voltage regulator is performed. That is, the direct current from the input terminal 10 is sent via the control transistor 31 and further via the boost-up diode 7 to the intermediate terminal 82 of the primary winding of the flyback transformer 8. Flyback transformer 8-1
A horizontal output transistor 61 is connected to the terminal 83 of the next winding, and the horizontal oscillator output is applied to the base of this transistor 61. Therefore transistor 6
1 periodically operates in a 0N10FF manner, and a voltage approximately proportional to the number of turns appears at each terminal of the primary winding of the flyback transformer 8. In this case, since 11V is applied to the intermediate terminal 82, a voltage of 22V, which is approximately twice that, is generated at the terminal 81. This output voltage is applied to the base of a comparison transistor 51 in the comparator 5 via a variable resistor 52 that constitutes a voltage dividing resistor for output voltage detection. transistor 5
A Zener diode 53 for obtaining a reference voltage is connected to the emitter of the transistor 1, and an error voltage between this reference voltage and the detected output voltage is fed back to the base of the control transistor 31 via the diode 33. The control transistor 31 changes the resistance between the collector and emitter according to the error voltage, and by changing the voltage drop across this transistor 31, the output voltage is set to a predetermined voltage, for example, 1.
The voltage is stabilized at 1V, and the output voltage at the terminal 81 is kept at a constant value, for example, 22V. Next, when connecting a DC power supply having an output voltage range of around 24V between the input terminals 10 and 11, the Zener diode 45 of the selection section 4 breaks down, and the power is supplied to the base of the transistor 42 via the Zener diode 45. Current is supplied. Therefore, the transistor 42 turns ON and the transistor 41 turns OFF. Therefore, the control transistor 31 of the low-voltage regulator becomes non-conductive, and the control transistor 21 of the high-voltage regulator becomes operative. The voltage stabilization operation is the same as described above, but in this case, one of the flyback transformers 8
No step-up operation is performed in the next winding, and the output voltage of the control section 2 is directly compared with the reference voltage in the comparison section 5, and the error voltage is fed back through the diode 23, and the output voltage is stabilized at 22V.

Note that it is also possible to adopt a configuration in which the output of the present DC stabilized power supply circuit is taken out from the intermediate terminal 82 of the primary winding of the flyback transformer 8.

In this case, the output voltage is always 11 regardless of the DC power supply voltage.
A stable voltage of V can be obtained. Further, in this case, the output voltage of the intermediate terminal 82 is detected and compared by the comparator. As is clear from the above explanation, the circuit uses a simple and inexpensive multiple transistor series control type regulator, and the internal resistance value of the control transistor of these multiple regulators is changed by one common comparison section. In addition, the regulation voltage range (range of voltage to be stabilized) of the control transistor of one regulator can be narrowed, which not only makes the circuit configuration simple and inexpensive, but also provides a highly efficient DC stabilized power supply circuit. can be provided.

Furthermore, since no chipper is used, there is no adverse effect such as high frequency interference. Furthermore, by reusing the horizontal output transistor that switches with the horizontal synchronization signal of the television receiver and the primary winding of the flyback transformer, it is possible to configure a DC/DC converter using the horizontal deflection output circuit, which simplifies the circuit. Parts can be shared, contributing to lower prices. Note that the present invention is not limited to the above-mentioned embodiment, and may be configured to selectively operate three or more regulator sections having different regulated voltage ranges, for example. Further, it goes without saying that the specific circuits such as the regulator section and the selection section are not limited to those shown in the drawings.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a block circuit diagram, and FIG. 2 is a circuit diagram showing an example of a specific configuration of FIG. 1. 10, 11... DC power input terminal, 2, 3...
...Regulator control section, 4...Selection section, 5...Comparison section, 6...DC-DC converter switching section, 7...・Boost up diode, 8...Flyback transformer.

Claims (1)

[Claims] 1: a plurality of transistor series control type regulator sections with different regulation voltage ranges; a selection section that detects DC input voltage and selectively operates one of the regulator sections; and a low voltage side regulator section among the regulator sections. and a DC-DC converter for converting the output voltage of the D into the output voltage of the high voltage side regulator section.
The C-DC converter is a primary of a flyback transformer, in which the output terminal of the high-voltage side regulator section is connected to one end thereof, and the output terminal of the low-voltage side regulator section is connected to its intermediate terminal via a rectifier. It consists of a winding and a horizontal output transistor connected to the other end of the primary winding and switched in response to a horizontal synchronization signal,
The plurality of transistor series control type regulator sections compare the output voltage generated at one end of the primary winding of the flyback transformer with a reference voltage, and control the control transistors of each regulator section according to the difference voltage. A DC stabilized power supply circuit for a television receiver, characterized in that it is controlled by one common comparison section that changes an internal resistance value.