JP2795995B2 - Stabilized power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilized power supply circuit suitable for supplying a driving DC voltage to a horizontal output circuit of a television receiver, for example.

[0002]

2. Description of the Related Art Conventionally, in a television receiver, a DC voltage for driving is supplied from a stabilized power supply circuit to a horizontal output circuit of the television receiver, and the supply voltage to the horizontal output circuit changes in input power supply voltage or high-voltage load current. It did not change due to fluctuations. More specifically, such a stabilized power supply circuit is configured as shown in FIG. 4, wherein 1 is an input terminal to which an unstable DC voltage obtained by rectifying and smoothing a commercial AC voltage is supplied, and 2 is a horizontal output circuit (not shown) A negative retrace period pulse (for extinguishing an SCR to be described later, that is, for turning off) is superimposed on a DC voltage from an input terminal 1 provided on the primary side of a flyback transformer for boosting and extracting a retrace period pulse from the SCR. The silicon for intermittently outputting a DC voltage from the input terminal 1 supplied from the input terminal 1 to the anode side of the winding 3 for pulse superposition to be turned on and off repeatedly through the winding 2 for pulse superposition on the anode side. The voltage output from the cathode side of the control rectifier (hereinafter, referred to as “SCR”) is supplied from an output terminal 4 to a horizontal output circuit. Reference numeral 5 denotes a start-up circuit that outputs a turn-on start-up pulse to the gate of the SCR 3 only at the start of voltage supply. Reference numeral 6 denotes a gate control circuit that outputs a turn-on control pulse to the gate of the SCR 3. The output timing is controlled according to the value of the output voltage output from the cathode side of the SCR 3.

Accordingly, the SCR 3 is turned on during a horizontal scanning period by a control pulse supplied to its gate after starting, and is turned off during a retrace period by a negative retrace period pulse supplied to its anode side. The turn-on timing is controlled based on the value of the output voltage from the cathode which tends to change in accordance with the change in the input voltage or the load. As a result, SCR
3, the voltage output from the cathode side is always kept constant except for the horizontal retrace period irrespective of fluctuations in the input voltage and the load. A stabilized DC voltage will be supplied.

[0004]

However, in such a stabilized power supply circuit having a conventional configuration, if the power consumption increases with an increase in the size of the screen of the receiver, the amount of heat generated in the SCR increases. It was necessary to take various measures against heat radiation, such as enlarging the plate, and the element capacity of the SCR was limited to a large one. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a stabilized power supply circuit that reduces the amount of heat generated in an SCR and provides a wide range of element capacitance selection. .

[0005]

In the present invention in order to achieve the above object, there is provided a means for solving] The non-stable DC voltage, on, in the stabilized power supply circuit for supplying a load after stabilization through the switching element to repeat off, the The switching element is
An unstable DC voltage superimposes a turn-off pulse.
Series supplied to the anode side through the winding for
Control rectifier element.
Two stages are connected in parallel, and the gate of one silicon
The voltage corresponding to the voltage output from the cathode side.
1st output of control pulse for turn-on
Gate control circuit and one silicon controlled rectifier element
When the current output from the load side exceeds a predetermined value,
The other silicon controlled rectifier at the timing according to the flow value
Output a control pulse for turn-on to the gate of the second
This is a configuration provided with a gate control circuit.

[0006]

According to this structure, the amount of heat generated by each SCR is reduced by the number of the plurality of SCRs, and one of the SCRs is supplied with a voltage.
And the other SCR is controlled based on the current.
When the load exceeds the specified current, the other
SCR can handle the current that exceeds the specified value.
It can prevent the destruction of one SCR
In both cases, set the other SCR to the current region near the upper limit of the capacity.
Can work. In this case,
Depending on the constant value, one SCR is also in the current range near the upper limit of the capacity
Can work up to.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. The same parts as those in the related art are denoted by the same reference numerals and description thereof will be omitted. In this embodiment, as shown in FIG. 1, the combination of the above-described pulse superimposing winding 2 and SCR 3 and gate control circuit 6 is combined with another stage pulse superposing winding 7 and SCR 8 and its gate control circuit 9. The combination of the current detection circuits 10 is connected in parallel, and the activation of the added SCR 8 is performed by detecting that the current output from the cathode side of the SCR 3 has been activated by the activation circuit 5 and has become a predetermined value or more. The detection by the circuit 10 causes the gate control circuit 9 to perform the detection. Here, the gate control circuit 9 controls the output timing of the control pulse supplied to the gate of the SCR 8 based on the value of the output current equal to or greater than a predetermined value detected by the current detection circuit 10.

Accordingly, only the SCR 3 is activated by the activation circuit 5 at the start of the voltage supply, and after the activation, the SCR 3 is turned on during the horizontal scanning period by the control pulse supplied from the gate control circuit 6 to the gate thereof, and the anode side is turned on. Is turned off during the retrace period by the negative retrace period pulse supplied to the switch, and the turn-on timing is controlled based on the value of the output voltage from the cathode side. As a result, the voltage output from the cathode side of the SCR 3 is always kept constant except for the horizontal retrace period irrespective of the fluctuation of the input voltage and the load, and usually the SC
Using only R3 (ie, single drive), a stabilized DC voltage is supplied from the output terminal 4 to the horizontal output circuit for driving the horizontal output circuit. In this state, the load becomes heavy due to, for example, an increase in the beam current of the picture tube, and S
In order to keep the output voltage on the cathode side of CR3 from decreasing, the turn-on timing of SCR3 is advanced, and when the output current increases to a predetermined value or more, this is notified to the current detection circuit 10. Will be detected. Therefore, the supply of the control pulse from the gate control circuit 9 to the gate of the SCR 8 is started, and the SCR 8 is also turned on. The turn-on timing is a current value equal to or more than a predetermined value detected by the current detection circuit 10. Will be controlled based on the Therefore, SCR
Numerals 3 and 8 are simultaneously turned off during the retrace period by a retrace period pulse supplied to the anode side of the negative polarity, and are horizontally scanned by control pulses from the gate control circuits 6 and 9 supplied to the respective gates. It is turned on during the period, and the turn-on timing is controlled based on the values of the output voltage and output current from the cathode side. As a result, only when the current output from the cathode side of the SCR 3 increases in this way, the voltage output from the cathode side is used to change the input voltage and the load by using the SCR 8 in parallel (by parallel driving). Regardless of the horizontal flyback period, it will always be kept constant,
The amount of heat generated in 3 and 8 is also reduced by the amount of current distributed by the parallel connection.

FIG. 2 shows an example of a specific circuit configuration of FIG.
Numeral 11 rectifies and smoothes the commercial AC voltage from the AC insertion plug 12 with the bridge type rectifier 13 and the smoothing capacitors 14 and 15 and the choke coil 16 and superimposes a pulse on the anode side of the SCRs 3 and 8 as an unstable DC voltage (Ein). Power supply circuit supplied through windings 2 and 7 for
A horizontal output circuit that is activated when a stabilized DC voltage (Eout) is supplied from the cathode side of R3 and 8 via a capacitor 18 and a primary winding of a flyback transformer described later. Reference numeral 19 denotes a horizontal oscillation circuit. , A horizontal deflection coil to which a deflection current is supplied by turning on and off the horizontal output transistor 19, 21 a damper diode, 22 a resonance capacitor, and 23 an S-shaped correction capacitor. It is. Reference numeral 24 denotes a retrace period pulse supplied from the horizontal output circuit 17 to the primary winding 24A, and the secondary winding 24B
This is a flyback transformer that further boosts the voltage, rectifies it with the high-voltage rectifier diode 25, and supplies the rectified voltage to the picture tube as an anode voltage. Reference numerals 26 and 27 denote commutation prevention circuits for preventing irregular turn-on not depending on the gate driving of the SCRs 3 and 8. Here, the gate control circuits 6 and 9 of the SCRs 3 and 8 rectify and smooth the pulse (synchronous with the retrace period pulse) generated in the tertiary winding 28 provided on the secondary side of the flyback transformer 24 by the diode 29 and the capacitor 30. Is supplied as an operating power supply voltage. The gate control circuits 6 and 9 are connected to the tertiary winding 2.
The first transistor 35 superimposes the output voltage (Eout) from the cathode side and the control voltage from the current detection circuit 10 on the charging voltage of the capacitors 33 and 34 supplied with the pulse from the resistor 8 through the resistors 31 and 32, respectively. , 36, and the second superimposed voltage is supplied to the base and operation is controlled.
The transistors 37 and 38 and the second transistor 3
The gate control circuit 6 controls the SCR 3 by controlling the voltage of the SCR 3 by controlling the operation of the SCR 3 and the gates of the SCRs 3 and 8 and outputting a turn-on pulse to the gates of the SCRs 3 and 8. The gate control circuit 9 controls the current of the SCR 8. Here, when the current output from the cathode side of the SCR 3 exceeds a predetermined value, the current detection circuit 10 converts the current higher than the predetermined value into a voltage corresponding to the value and outputs the voltage as a control voltage. When it is detected that an abnormal current is flowing from the cathode side, the overcurrent protection circuit 43 is activated and the power switch 44 is opened by a power relay (not shown). Also SCR
3 includes a resistor 45 and a Zener diode 46.
And a backflow prevention diode 47 connected in series, for example, a resistor 45, a diode 47 and an SCR.
If the voltage drop between the gate and cathode of the transistor 3 is neglected, its operation depends on the potential difference between the input voltage (Ein) and the output voltage (Eout) and the Zener voltage Vz of the Zener diode 46, and when Ein−Eout> Vz is satisfied. A current flows and the SCR 3 is automatically activated.

Therefore, when the power supply switch 44 is closed and the power supply is started, the SCR 3 is activated by the activation circuit 5 and turned on, the capacitor 18 is charged by the output voltage from the cathode side, and the activation by the activation circuit 5 is stopped. At the same time, the horizontal output circuit 17 is activated to generate a retrace period pulse, and the retrace period pulse is boosted by the flyback transformer 24. At this time, the pulses from the tertiary winding 28 (see FIG. 3A) activate the gate control circuits 6, 9 respectively, and also charge the capacitors 33, 34. for that reason,
The gate control circuit 6 controls the first transistor 3 in the active state.
5, the voltage at point P1 (see the solid line in FIG. 3B) on which the output voltage from the SCR 3 is superimposed.
Is turned on for the period indicated by the solid line in FIG. 3C, the third transistor 41 is momentarily turned on by a negative pulse (see FIG. 3D) obtained from the differentiating circuit 39, and FIG.
The control pulse as shown in FIG. The control pulse from the gate control circuit 6 is SCR3
Will be supplied to the gate. At this time, SCR3
Is less than a predetermined value, and the current detection circuit 10
Outputs a control voltage for forcibly setting the first transistor 36 to the ON state.
Is such that the voltage at point P2 does not exceed the threshold level for turning on the second transistor 38, and no control pulse is output. Therefore, the SCR 8 is not turned on, and the single drive of only the SCR 3 is performed. Therefore, the turned-on SCR 3 is turned off in the retrace period by the retrace period pulse supplied to the anode side of the negative polarity, and thereafter the SCR 3 is turned on by the gate control circuit 6 and turned off by the winding 2 for pulse superposition. The turn-on timing is controlled based on the value of the output voltage from the cathode side. For example, when the output voltage increases due to a decrease in the beam current of the picture tube, the first transistor 3
5 is reduced and the voltage at the point P1 is reduced as shown in FIG.
Since the voltage drops as indicated by the dotted line, the second and third transistors 3
The turning on of the switches 7 and 41 is sequentially delayed as shown by the dotted lines in FIGS. 3C and 3E, and the control pulse output from the gate control circuit 6 is also delayed. Therefore, the turn-on timing of the SCR 3 is delayed, and the voltage output from the cathode side of the SCR 3 decreases. As a result, the output voltage (Eout) from the SCR 3 is always kept constant, and a stabilized DC voltage is always supplied to the horizontal output circuit 17 for its operation.

If the load becomes heavy due to an increase in the beam current of the picture tube in this state, the turn-on timing of the SCR 3 is advanced to compensate for the decrease in the output voltage, and the output current increases to exceed a predetermined value. When this happens, the current detection circuit 10 detects this fact, and outputs a control voltage for turning the first transistor 36 from the ON state to the active state. The control voltage is further varied according to a current value equal to or greater than a predetermined value, for example, the current As the value increases, the control voltage decreases accordingly. Therefore, the gate control circuit 9 supplies the current detection circuit 1 via the active first transistor 36.
The voltage at the point P2 on which the control voltage from 0 is superimposed, and the second and third transistors 38, 38 as in the case of the gate control circuit 6.
By turning on 42, a control pulse is supplied to the gate of SCR8 to turn on SCR8. Then, the turned-on SCR 8 is turned off at the same time as the SCR 3 by a negative retrace period pulse supplied to the anode side thereof, and thereafter the SCR 8 is turned on while the output current is equal to or higher than a predetermined value. And the turn-off by the pulse superimposing winding 7 are alternately repeated. The turn-on timing is based on the value of the output current from the cathode side. For example, when the output current increases, the timing becomes earlier. Will be controlled. In this embodiment, the case where the combination of the coil for pulse superposition, the SCR and the gate control circuit is connected in two stages is described. However, the number may be more than that and the SCR is used as the switching element. The case was mentioned, but is not limited to this.
The configuration of the gate control circuit is not limited to this. Further, instead of the horizontal output circuit, a pseudo retrace period pulse from a pulse generation circuit having a similar configuration to the horizontal output circuit may be used, and the SCR is always driven in parallel by voltage and current control. You may do it.

[0012]

As described above, according to the stabilized power supply circuit of the present invention, when the output current increases due to, for example, an increase in the beam current of the picture tube, the SC as the switching element is used.
By using a plurality of Rs connected in parallel, each S
The amount of heat generated in the CR can be reduced, and each S
The CR is controlled by a gate control circuit , one based on the voltage,
Is controlled based on the current, so that the element capacity of the SCR can be efficiently selected. Also, like this
The other SCR is controlled based on the voltage, and the other SCR is controlled based on the current.
By controlling the load based on the
When the other SCR exceeds the specified value
Can be in charge, thereby breaking one SCR
Can prevent breakage and use the other SCR as the upper limit of ability
It is possible to operate up to a near current region.
In this case, one of the SCRs will have higher performance depending on the specified value.
Operation up to the current range close to
You.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a specific circuit configuration example.

FIG. 3 is an operation waveform diagram thereof.

FIG. 4 is a block diagram showing a conventional example.

[Explanation of symbols]

 2, 7 Pulse superposition winding 3, 8 SCR 5 Starter circuit 6, 9 Gate control circuit 10 Current detection circuit

Claims (1)

(57) [Claims] The method according to claim 1] non-stable DC voltage, on, in the stabilized power supply circuit for supplying a load after stabilization through the switching element to repeat off, the switching element is non
A pulse with a stable DC voltage superimposed with a turn-off pulse
Silicon supplied to the anode side through the superposition winding
Control rectifier element.
Connected in parallel with the gate of one silicon controlled rectifier
To the cathode according to the value of the voltage output from the cathode side.
Output the control pulse for turning on the
Control circuit and one silicon-controlled rectifier element
When the current output from the
At the timing according to the value of the other silicon controlled rectifier.
A second gate that outputs a control pulse for turn-on to the gate
A stabilized power supply circuit,
Road.