JPH10210388A - Power circuit for television receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution and also to stabilize the operation in a standby mode for a power circuit of a TV receiver, which performs the switching between the normal and standby operations. SOLUTION: When a microcomputer 24 outputs a control signal to switch a normal operation to a standby operation, a power oscillation stop circuit 40 acts on a control terminal (F/B) of a power controller 3 to stop the oscillation of an FET 4 for a fixed period and to open a switch circuit 22. A 5V regulator 23 functions to keep the power voltage applied to the power terminal of the microcomputer 24 at a prescribed level. A voltage maintenance circuit 39 maintains the input voltage that is applied to the 5V regulator 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit for a television receiver which switches between a normal operation and a standby operation.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a horizontal deflection high voltage generating circuit of a television receiver. In FIG. 4, a horizontal deflection circuit 36 surrounded by a broken line includes a horizontal drive transistor 28, a horizontal drive transformer 29, a drive resistor 30,
Horizontal output transistor 31, damper diode 32,
It comprises a resonance capacitor 33, a horizontal deflection coil 34, and an S-shaped correction capacitor 35. This horizontal deflection circuit 3
The horizontal pulse generation circuit 27 is connected to the stage preceding the line 6. The voltage BL is input to the horizontal pulse generation circuit 27,
A horizontal pulse is supplied to the base of the horizontal drive transistor 28. A flyback transformer 37 is connected to a stage subsequent to the horizontal deflection circuit 36, and a cathode ray tube 38 is connected to the flyback transformer 37.

In such a configuration, when the horizontal output transistor 31 performs a well-known switching operation, a pulse voltage is generated at a point A in FIG. This pulse voltage is boosted by a flyback transformer 37 and a high voltage is supplied to a cathode ray tube 38.

Here, assuming that the voltage of the input voltage + B to the horizontal deflection circuit 36 and the flyback transformer 37 is Eo, the capacitance of the resonance capacitor 33 is C, the inductance of the horizontal deflection coil 34 is L, and the horizontal oscillation frequency is th. The pulse voltage Ep on the primary side of the flyback transformer 37 is generally expressed by the following equation (1).

[0005]

(Equation 1)

Assuming that the turns ratio of the primary side / secondary side of the flyback transformer 37 is np / ns, the pulse voltage Es (which is substantially equal to the high voltage value) on the secondary side of the flyback transformer 37 is as follows: 2) It is expressed by the equation. Es = (ns / np) · Ep (2)

From the equations (1) and (2), the pulse voltage Es is
It is expressed by the following equation (3).

[0008]

(Equation 2)

As can be seen from the equation (3), the high voltage value is proportional to the input voltage + B. That is, the input voltage + B
If the pressure drops, the high pressure value drops.

FIG. 3 is a circuit diagram showing an example of a power supply circuit of a conventional television receiver. In the standby state of the television receiver, the output voltage is made lower than that in the normal operation and the input to the horizontal deflection high voltage generating circuit is made. The voltage + B is reduced to reduce the residual high voltage.

In FIG. 3, 1 is a rectifying and smoothing circuit, 2 is a starting resistor, and 3 is a power supply controller. First, during normal operation, the FET 4 performs a switching operation, and the transformer 9 operates.
In each winding, a voltage corresponding to the number of turns of the winding is excited. Voltages generated in the windings 9b1, 9b2, 9b3 on the secondary side of the transformer 9 are connected to diodes 11, 13, 15 and capacitors 12, 14, 16 connected to the windings 9b1, 9b2, 9b3, respectively.
Rectified and smoothed to obtain a DC voltage.

The DC voltage + B generated by the winding 9b1 of the transformer 9 and rectified and smoothed by the diode 11 and the capacitor 12 is supplied to the power supply via the photocoupler 10 by the error amplifier 19 so that the voltage + B becomes constant at the voltage value Eo. It is fed back to the feedback terminal (F / B) of the controller 3. Then, the ON width of the pulse output from the drive terminal (DRIVE) of the power supply controller 3 is controlled, and the FET 4 is driven by this pulse, so that the voltage + B is stabilized. OCP of the power controller 3 is an overcurrent protection terminal.

Reference numerals 17, 21, and 22 denote switch circuits that are short-circuited when the control input goes high and open when the control input goes low. During normal operation, the microcomputer (microcomputer) 24 outputs a high signal from the power terminal (PW). Therefore, the control input of the switch circuit 17 becomes low due to the inversion circuit 26, and the switch circuit 21 is opened, and the switch circuits 21 and 22 are short-circuited. Switch circuit 2
2 is short-circuited, the voltage BL is supplied to the small signal circuit such as the horizontal pulse generation circuit 27 in FIG. 4, and the short-circuiting of the switch circuit 21 causes the error amplifier circuit 20 of the voltage BL to be in a non-operation state. Become.

On the other hand, when a standby command is input from a remote control transmitter (not shown) to the remote control light receiving unit 25, the command is input to the remote control terminal (RC) of the microcomputer 24, and the microcomputer 24 is set to a low level from the power terminal. Output a signal. Therefore, the switch circuit 17 is short-circuited when the control input becomes high by the inverting circuit 26, and the switch circuit 2
1 and 22 are open.

The voltage value of voltage + B at the time of standby is 1 / M (M>) of the voltage value of voltage + B at the time of normal operation.
0), the winding number of the winding 9b2 of the transformer 9 is
And the number of turns of the winding 9a2 is set to be M times or more the number of turns of the winding 9a3. The error amplifier circuit 20 is set so that the point C in FIG. 3 becomes the voltage E1 during the normal operation of the voltage BL. Then, as described above, when the switch circuit 17 is short-circuited and the switch circuits 21 and 22 are opened, the feedback loop is switched from the error amplifier 19 to the error amplifier circuit 20, and the voltage + B is kept constant at the voltage Eo. Is fed back to the power supply controller 3 so that the voltage at the point C becomes the voltage E1.

Therefore, during standby, the voltage + B
Becomes 1 / M, and as described with reference to FIG. 4, the high voltage value also decreases to about 1 / M. However, during standby, the voltage E1 cannot be supplied from the winding 9b3 of the transformer 9 since the voltage E1 cannot be supplied from the winding 9b3.
A power supply terminal of the microcomputer 24 (V
cc). For the same reason, during standby, the power supply voltage E2 for driving the power supply controller 3 cannot be supplied from the winding 9a3. Therefore, the voltage E2 is supplied from the winding 9a2 via the backup circuit 5 to the power supply terminal (Vcc). ) Supplied.

[0017]

In such a configuration, since the transformer 9 requires the windings 9a2 and 9b2 other than the power supply for standby, the size of the transformer is increased and the number of pins is increased. As the number increases, the material cost increases, and the degree of freedom in selecting a transformer decreases. Furthermore, since the backup circuit 5 for the power supply controller 3 and the backup circuit for the voltage BL, such as the diode 13, the capacitor 14, and the switch circuit 17, are also required, a large board space is required and the material cost is high. There are points.

As a power supply circuit of a television receiver which solves this problem, there is a power supply circuit described in Japanese Patent Application Laid-Open No. 7-38824. In this power supply circuit, a CPU (see FIG. Microcomputer 2 in 3
(Equivalent to 4) could not be maintained at 5V, and the CPU might be reset, which was a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and can simplify the configuration of a power supply circuit of a television receiver that switches between normal operation and standby operation, and can also operate in standby mode. An object of the present invention is to provide a stable power supply circuit of a television receiver.

[0020]

According to the present invention, a first winding (9b1) for generating a first voltage to be supplied to a flyback transformer (37) is provided. , A second winding (9b) for generating a second voltage having a smaller voltage value than the first voltage supplied to the small signal circuit.
3) a switching element for supplying a pulse to the primary side of the transformer for driving the transformer, and a pulse width of a pulse generated by the switching element. In a power supply circuit of a television receiver having a controller (3) and a microcomputer (24) for switching between normal operation and standby operation, when a control signal for switching to standby operation is input from the microcomputer, the controller A power supply oscillation stop circuit (40) that acts on the control terminal of the power supply to stop the oscillation of the switch element for a certain period of time; and a switch circuit that cuts off the supply of the second voltage to the small signal circuit by the control signal ( 22) and before being provided between a power supply terminal of the microcomputer and the second winding of the transformer. A regulator (23) for maintaining the power supply voltage to the power supply terminal of the microcomputer at a predetermined voltage;
And a voltage maintaining circuit (39) provided between the regulator and the second winding of the transformer for maintaining an input voltage to the regulator. Is provided.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power supply circuit of a television receiver according to the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a circuit diagram showing one embodiment of a power supply circuit of a television receiver of the present invention, and FIG. 2 is a waveform diagram for explaining one embodiment of a power supply circuit of the television receiver of the present invention. In FIG. 1, the same parts as those in FIG. 3 are denoted by the same reference numerals.

The configuration of FIG. 1 of the present invention is different from the configuration of FIG. 3 of the prior art in that the backup circuit 5, the windings 9a2 and 9b2 of the transformer 9, the diode 13, the capacitor 14, the switch circuits 17 and 21, and the error amplifier circuit 20 , Inverting circuit 26
And a voltage maintaining circuit 39 and a power oscillation stop circuit 40 are newly provided.

First, during normal operation, the FET 4 as a switching element performs a switching operation, and a voltage corresponding to the number of windings of each winding of the transformer 9 is excited. The voltage generated in the windings 9b1 and 9b3 on the secondary side of the transformer 9 is
Diodes 11 and 15 and capacitors 12 and 16 connected to b1 and 9b3 respectively perform rectification and smoothing to obtain a DC voltage.

The DC voltage + B generated by the winding 9b1 of the transformer 9 and rectified and smoothed by the diode 11 and the capacitor 12 is supplied to the power supply via the photocoupler 10 by the error amplifier 19 so that the voltage + B becomes constant at the voltage value Eo. It is fed back to the feedback terminal (F / B) of the controller 3. Then, the ON width of the pulse output from the drive terminal (DRIVE) of the power supply controller 3 is controlled, and the FET 4 is driven by this pulse, so that the voltage + B is stabilized. OCP of the power controller 3 is an overcurrent protection terminal.

Reference numeral 22 denotes a switch circuit which is short-circuited when the control input goes high and opened when the control input goes low. During normal operation, the microcomputer (microcomputer) 24 outputs a high signal from the power terminal (PW). Therefore, the switch circuit 22 is short-circuited.
When the switch circuit 22 is short-circuited, the voltage BL is supplied to a small signal circuit such as the horizontal pulse generation circuit 27 in FIG. The voltage value of the voltage BL is smaller than the voltage value of the voltage + B.

On the other hand, when a standby command is input from a remote control transmitter (not shown) to the remote control light receiving unit 25, the command is input to the remote control terminal (RC) of the microcomputer 24, and the microcomputer 24 is set to a low level from the power terminal. Output a signal. Therefore, the switch circuit 22 is open.

As shown in FIG. 2A, at time t1, when the microcomputer 24 outputs a low signal from the power terminal (point H), the transistor 43 in the power oscillation stop circuit 40 is turned off, The voltage at the point is shown in FIG.
It rises as shown in (B). When the charging of the capacitor 42 is completed, the voltage at the point E decreases and becomes 0 at time t2. During this time, the transistor 44 is turned on, a large current flows through the photodiode 10a of the photocoupler 10, and an excessively large current flows through the phototransistor 10b as compared with the constant voltage control.

Then, a large current flows into the feedback terminal of the power supply controller 3, so that the ON width of the pulse output from the drive terminal is controlled to be small. Then, as shown in FIG. 2C, the FET 4 stops oscillating until time t2 when the charging of the capacitor 42 is completed and the power supply controller 3 is restarted. Therefore, the voltage + B starts to decrease from time t1, as shown in FIG. 2D, and rises again to the voltage Eo when the power supply controller 3 is restarted.

Further, since the switch circuit 22 is opened and the supply of the voltage BL to the small signal circuit such as the horizontal pulse generation circuit 27 in FIG. 4 is cut off, the output pulse of the horizontal pulse generation circuit 27 stops. As shown in FIG. 2E, the base waveform of the horizontal output transistor 31 in FIG.
From time t1, the amplitude decreases and the operation stops. Accordingly, as shown in FIG. 2 (F), the high voltage to the cathode ray tube 38 falls from time t1 and the oscillation of the horizontal output transistor 31 stops, so that the high voltage does not rise again.

Further, the voltage at point D in FIG.
As shown in (G), since the voltage falls from time t1 to time t2, the 5V regulator 23 and the diode 15 are connected so that the power supply terminal (voltage at point G) of the microcomputer 24 does not decrease.
A voltage maintaining circuit 39 is provided between the rectifying / smoothing circuit of the capacitor 16 and the input voltage of the 5V regulator 23. As shown in FIG. 2H, the input voltage of the 5V regulator 23 (the voltage at the point F) slightly decreases from time t1 to t2 due to the power supply to the microcomputer 24, but the output of the 5V regulator 23 Voltage (voltage at point G)
Is constant as shown in FIG. 2 (I).

Therefore, in the configuration of FIG. 1 of the present invention,
The danger that the power supply terminal of the microcomputer 24 falls below 5V and the microcomputer 24 is reset can be reliably avoided.

[0032]

As described above in detail, the power supply circuit of the television receiver of the present invention operates on the control terminal of the controller of the power supply when the control signal for switching to the standby operation is input from the microcomputer. A power supply oscillation stop circuit that stops the oscillation of a switch element that supplies a pulse to the transformer for a certain period, a switch circuit that shuts off the supply of voltage to the small signal circuit by a control signal, and a power supply terminal of the microcomputer and the transformer. A regulator provided between the power supply terminal of the microcomputer and a power supply terminal for maintaining a predetermined voltage, and a voltage maintenance circuit for maintaining an input voltage to the regulator provided between the regulator and the transformer are provided. The configuration can be simplified, and the microcomputer is inadvertently reset during standby. No Rukoto, it is possible to stabilize the operation in the standby.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining one embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional example.

FIG. 4 is a circuit diagram showing a horizontal deflection high voltage generation circuit.

[Explanation of symbols]

 Reference Signs List 3 power supply controller 4 FET (switch element) 9 flyback transformer 9a1, 9a3, 9b1, 9b3 winding 22 switch circuit 23 5V regulator 24 microcomputer 39 voltage maintenance circuit 40 power supply oscillation stop circuit

Claims (1)

[Claims] 1. A first winding for generating a first voltage to be supplied to a flyback transformer, and a second winding for generating a second voltage having a smaller voltage value than the first voltage to be supplied to a small signal circuit. A switching element that supplies a pulse to the primary side of the transformer to drive the transformer, a controller that controls a pulse width of a pulse generated by the switching element, and a normal operation. And a microcomputer that switches between a standby operation and a standby operation. When a control signal for switching to a standby operation is input from the microcomputer, the control signal of the switch element is acted on a control terminal of the controller. A power oscillation stop circuit for stopping oscillation for a certain period of time; A switch circuit for interrupting supply of a voltage, a regulator for maintaining a power supply voltage to a power supply terminal of the microcomputer provided between a power supply terminal of the microcomputer and the second winding of the transformer at a predetermined voltage, A power supply circuit for a television receiver, comprising: a voltage maintaining circuit provided between the regulator and the second winding of the transformer for maintaining an input voltage to the regulator.