JPH0514472B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention relates] The present invention relates to the standby operation of a television receiver, and more particularly to a power source for supplying power to a remote control circuit within the television receiver during standby operation. This invention relates to a return drive type mains power supply, particularly as disclosed in British Published Patent Specification No.
Single conversion method (SICOS) as described in issue 2094085A
(i.e., a system in which unregulated AC voltage is converted to regulated AC voltage and supplied as the power supply voltage).

[Prior art]

Several types of standby circuits for television receivers are known, including a small AC line voltage transformer that supplies power to the television receiver's remote control circuitry and a relay that switches the television receiver on and off. Although some standby circuits of this type consume only about 6 watts, they are relatively expensive as standby power supplies.

Another type of standby circuit is a switched mode power supply with an integrated circuit controller, such as the TDA4600, and a relay that interrupts most of the secondary voltage during standby.
This switched-mode power supply operates at approximately 70KHz to provide the wide adjustment range required during standby, but its power consumption during standby is relatively high at 10 to 20 watts.

Yet another type of standby circuit is a mains transformer coupled to a switched mode regulator without a relay.
Although the horizontal oscillator is deenergized by the remote control circuit during standby, using a mains transformer is a relatively cumbersome method of designing the standby circuit.

[Disclosure of the invention]

A feature of the standby circuit of the present invention is that standby operation is initiated by shorting the horizontal sweep switch, for example by keeping the horizontal output transistor in continuous saturation during standby. When using a mains power supply such as the SICOS type power supply described above, a short circuit in the sweep switch causes the power supply to self-spark around the horizontal deflection frequency with a shock factor approximately equal to the ratio of the sweep (trace) period to the retrace period (retrace). Causes running oscillation. The power for the standby remote control circuit flows from the flyback transformer through the shorted sweep switch, and the power consumption during this standby is less than 10 watts, typically about 6 watts, and the power available for the remote control circuit is Approximately 1.5 watts at 12 volts is sufficient.

[Embodiments of the invention]

In FIG. 1, a SICOS type power supply 20 described in the above-mentioned British published patent specification has a high voltage winding W to which a high voltage anode load 33 is coupled from an unregulated B+ power supply terminal.
It serves to deliver power to the various load circuits of the television receiver which are coupled to the secondary windings of the flyback transformer T1, including the transformer T1. During normal mode operation, the horizontal retrace pulse voltage V3 of FIG. 2c generated by the horizontal deflection generator 21 is applied to the flyback transformer T.
1 is transformer coupled from the secondary winding W2 to the primary winding W1.

The positive retrace pulse from the tap of primary winding W1 is peak rectified by diode D1, filtered by capacitor C1, and passed through signal line 34.
applied to the SICOS regulator control circuit 22. The regulator control circuit 22 is synchronized with the horizontal deflection by a retrace pulse voltage applied via a signal line 29 and produces a pulse width modulated signal 23 whose duty factor varies with changes in the amplitude of the retrace pulse voltage. This pulse width modulated signal 23 is applied to the input terminal 24 of the SICOS type power supply 20 and is applied to the push-pull switch S1,
Pulse modulate S2. This switch includes a transistor Tr1 or Tr2, each having an anti-parallel diode (not shown) between the collector and emitter, and pulse width modulates the operation of switches S1 and S2 to adjust the retrace pulse amplitude to the load and B+
It is designed to remain relatively constant as voltage conditions change.

The positive voltage developed across capacitor C1 keeps transistor Q1 in saturation, thereby bringing its collector voltage to the potential of ground 25 and across diode D10.
to reverse bias. Flyback transformer T1-2
On the next side, the standby switching transistor Darlington transistor Q2 connects the holding line 26 to the resistor R.
9 and the base current flowing through the Zener diode D5. For this purpose, horizontal sweep switch 27 and horizontal drive transistor Q5 are connected to chassis ground point 28 via remote control switch Q2 which is conducting.

The waveforms in FIGS. 2a to 2e show the normal mode operation of the SICOS power supply and horizontal deflection circuit in FIG.
This is the switching voltage V1 at the connection point of S2. The dashed waveform in FIG. 2 shows the adjustment range of the power supply, and the solid waveform shows the waveform taken at the normal operating point of the power supply.

FIG. 4 shows a detailed embodiment of the circuit of the SICOS type power supply 20 of FIG. Switch S1 conducts at a controllable time _T4 during the sweep of the horizontal deflection cycle to couple energy storage inductor L1 to the B+ input voltage terminal. This switch S1 is a pulse width modulated signal 23
The rising edge of S2 turns on the transistor Tr4 near the time _T4 , thereby cutting off the transistor Tr2 of the switch S2. Main winding L1a of inductor L1
In order to maintain the current i ₁ of the winding L1a, the dot terminal of the winding L1a becomes positive with respect to the non-dot terminal, and the switch S1
The bias diode DS1 of DS1 is forward biased.
Therefore, a gradually decreasing current of the winding L1a flows to the B+ terminal in FIG.

The positive voltage at the dot terminal of the winding L1a is the control winding L1.
A positive voltage is induced at the dot terminal of c, and the transistor
Forward bias the base-emitter junction of Tr1.
The transistor Tr1 is connected to the current i ₁ in FIG. 2b at the time T ₄
Winding L1 becomes positive during the post-sweep period _T2 to _T6 .
Apply current to a.

At the end of the sweep period, at time _T6, a controllable amount of energy has been stored in inductor L1, and much of this stored energy is absorbed by the load coupled to flyback transformer T1 during horizontal retrace period _T6 - _T7 . transferred to the circuit.

At time _T6 , the positive retrace pulse voltage generated at the dot terminal of winding W1 of flyback transformer T1 is applied to the non-dot terminal of winding L1a of inductor L1, causing winding L1a and control winding L1b, Make the non-point terminal of L1c positive. Transistor Tr3 conducts and cuts off transistor Tr1. This causes a positive current to flow through the diode DS2 of the switch S2 until the current _i1 becomes negative near the center of the return line and the transistor Tr2 takes over conduction. That is, even if the transistor Tr1 is cut off, the current flowing into the dot terminal of the winding L1a is not immediately cut off, and the current flows through the diode DS2. 2 of the retrace inductor L1, the capacitor C _R , the horizontal deflection winding L _H and the flyback transformer T1.
A flyback transformer T is connected between the retrace resonant circuit consisting of the load circuit coupled to the next windings W3 and W4.
A resonant transfer of energy through 1 takes place.

Figure 2d shows the base current _i3 of the horizontal output transistor Q4 flowing from the dot terminal of the winding _Wb of the horizontal drive transformer T2, and Figure 2e shows the current i flowing through the winding _Wc of the drive transformer T2. Shows ₂ . Near time T ₀ , the horizontal drive transistor Q5 becomes conductive and turns in the opposite direction (winding
A base current i ₃ (direction flowing into the dot terminal of W _b ) is generated, and the horizontal output transistor Q 4 is cut off at time T ₁ . Also, the generation of current i ₂ begins near time T ₀ , and this flows through diode D2 to capacitor C.
Charge 8. Therefore, the current during normal mode operation
i ₂ and i ₃ are generated by the switching action of the horizontal drive transistor Q5.

To switch the television receiver to standby mode operation, a chassis ground potential is applied as an OFF command signal from the remote control circuit 30 to the remote control switching transistor Q2 via the control line 31 for about 1 second. When transistor Q2 is cut off, the current in winding W2 of flyback transformer T1, which had been flowing through transistors Q4 and Q2, flows through winding W _c of the horizontal drive transformer, diode D2, and transistor Q3 to chassis ground. 28 was swept away. That is, when a normal current i' ₁ flows out of the dot terminal of winding W2 of the flyback transformer, the return path of this current is through horizontal output transistor Q4 to the dot terminal of winding W _c of drive transformer T2. To enter the,
Furthermore, capacitor C8 is charged to a positive value via diode D2. Also, when the normal current i' ₁ flows out from the non-point terminal of the winding W2 of the flyback transformer, its return path is through the diode of the Darlington transistor Q2, the damper diode D7 of the sweep switch 27, and the horizontal output transistor Q4.
passes through a diode formed by the base-collector junction of .

The positive current i ₂ induces a positive base current i ₃ of the horizontal output transistor Q4 in the winding W _b of the horizontal drive transformer T2. The current _i3 is the horizontal output transistor Q
4 conductive, transformer T2 acts as a bootstrap transformer providing positive feedback from the output of its transistor Q4 to keep it in saturation.

During standby, transistor Q4 is in a saturated forward conduction state or in a reverse collector conduction state in which damper diode D7 is also conductive. That is, during standby, transistor Q2 is non-conducting and current flows through winding W2.
When flowing from the dot terminal of , via the transistor Q4 and the winding W _c , the current i ₂ flows through the winding W _c .
induces a voltage in winding W _b that maintains transistor Q4 in saturation. Furthermore, when a current flows into the dot terminal of the winding W2, the current flows from the ground point to the diode BD681 connected between the emitter and collector of the transistor Q2, the damper diode D7, and the diode formed by the base-collector junction of the transistor Q4. flows through. These conduction states actually cause the sweep switch 27
is shorted, connecting the dot terminal of winding W2 of the flyback transformer to the dot terminal of winding _Wc of the drive transformer. If this short-circuiting of the sweep switch 27 continues, the formation of a retrace resonant circuit is prevented, thereby reducing the retrace pulse voltage and no longer generating a retrace pulse. As a result, the supply current through the diodes D4, D6, the supply voltage _Vb and the current through the holding line 26 become zero. Therefore, the remote control transistor Q2 remains cut off even after the one second off command signal feedback period has elapsed.

The voltage V _a of the capacitor C4 is the voltage V a of the remote control circuit 30
and the supply voltage of the 12 volt supply line that energizes the horizontal oscillator 32. This voltage is generated via diodes D2, D3 from the positive current i' ₁ flowing as current i ₂ in the winding W _c of the drive transformer in the standby mode of operation. Horizontal oscillator 32 operates during standby to facilitate the television receiver's conduction switching as described below. Darlington transistor Q3 acts as a shunt regulator to limit the voltage on capacitor C8.

On the primary side of the flyback transformer _T1 , when the standby mode of operation begins, the retrace pulse is crushed, so that the SICOS type power supply 20 starts to operate in the free running mode. Control circuit 2 due to the collapse of the retrace pulse
2 no longer works, cutting off transistor Q1. In order to cut off this transistor Q1, the resistor R
The RC network including 1 to R4 and capacitor C2 is
Together with the SICOS switches S1 and S2, an astable multivibrator circuit can be constructed.

The waveform in Figure 3 shows the first waveform in standby mode operation.
This is related to the circuit shown in the figure. After time _t1 , switch S1 of the SICOS power supply 20 is conducting, as shown by voltage V1 in FIG. 3a. Since the left plate of capacitor C2 becomes positive with respect to the right plate near time _t1 , when switch S1 becomes conductive, capacitor C2 increases to the gradually decreasing voltage V2 at the collector of transistor Q1 after time _t1 as shown in FIG. 3b. Thus, as shown, discharge begins via resistors R2 and R3.

The switch S1 of the SICOS type power supply 20 remains conductive due to the regenerative action of the control windings L1b and L1c of FIG. 4, and its transistor is turned on as shown in FIG. 3a.
Conduction continues until time t ₃ when Tr1 begins to shut off.
Note that since the current flowing into the dot terminal of the winding L1a generates a positive voltage at the dot terminal of the control winding L1c, the transistor Tr1 is biased in the forward direction until the transistor Tr3 becomes conductive. At time _t4 , the transistor Tr1 is cut off, the switch S2 becomes conductive due to the conduction of the diode DS2, and the voltage V1 becomes ground potential.

By time _t4 , capacitor C2 charges to a voltage of opposite polarity such that the right plate of the capacitor becomes positive with respect to the left plate. When the positive right plate of capacitor C2 is fixed to ground voltage by switch S2, voltage V2 is brought to ground voltage between times t ₄ and t ₆ in FIG. 3b when the base-collector junction of transistor Q1 is forward biased. Keep it slightly lower. During these periods t ₄ and t ₆ , capacitor C2 discharges from the B+ terminal via the base-collector junction of transistor Q1 and resistor R2, and around time t ₆ the polarity of the voltage across capacitor C2 is reversed to Reverse bias the collector junction. Capacitor C2 begins charging from the B+ terminal, with its left plate becoming positively charged relative to its right plate.

By time _t7 in FIG. 3b, capacitor C2 is sufficiently charged to forward bias diode D10 and control transistor Tr4 of SICOS type power supply 20.
conduction. Note that since the current flowing out from the dot terminal of the winding L1a generates a positive voltage at the non-dot terminal of the control winding L1b, the transistor Tr2 is biased in the forward direction until the transistor Tr4 becomes conductive. When the control transistor Tr4 becomes conductive, the output switching transistor Tr2 is cut off.
When Tr2 is cut off, the diode of switch S1
DS1 becomes conductive and the main winding L of the inductor L1 in Fig. 4
Take out the current from 1a. Voltage V1 therefore rises to the B+ voltage level shown in FIG. 3a. Note that the diode DS1 conducts when the transistor Tr
This is because the current flowing out from the dot terminal of the winding L1a is not immediately cut off even if the winding L1a is cut off.

The length of one cycle of free-running oscillation of switches S1 and S2 is, for example, 70 μs, and the length of the horizontal deflection period T _H
Close to 64 microseconds. This free-running period of 70 microseconds is chosen to be short enough so that most people cannot hear it in standby mode. This free-running period can be adjusted by adjusting the value of the resistor R2 of the astable multivibrator.

Figure 3c shows the flyback transformer _T1 in standby operation.
The current flowing through the winding W1 is shown. Winding wire W1, W2
are tightly coupled to each other and the number of turns is approximately equal, so that the current i' 1 flowing in the winding W2 and thus the collector of the horizontal output transistor Q4 in standby mode is equal to the current _{i 1}
It has almost the same shape and amplitude as . Since the currents i ₁ , i′ ₁ during standby mode operation are substantially smaller than those during normal mode operation, the
The power consumption of the SICOS type power supply 20 is relatively low,
For example, it is 6 watts.

FIG. 3d shows the voltage V4 across the remote control switching transistor Q2 during standby operation. During the period _t0 to _t2 when the currents in windings W1 and W2 of flyback transformer _T1 are negative, diode BD681 of Darlington transistor Q2 is forward biased to fix voltage V4 to chassis ground potential. period t ₂
At ~ _t3 , the current _i1 , _1'1 is positive and slopes upward to the right.
During this period the current i ₂ in the winding W _c of transformer T2 is positive;
Forward bias diode D2 and capacitor C8
to a voltage of approximately 20 volts. During this period, voltage V4 is positive and fixed at the voltage level set by the voltage developed across winding W _c of drive transformer T2 and capacitor C8.

The switch S2 of the SICOS type power supply 20 conducts around the time t ₃ and starts a negative slope of the currents i ₁ , i' ₁ . From time t ₃ onwards, the current i' ₁ flowing through the winding W _c of the drive transformer T2 reverses the polarity of the voltage developed in that winding W _c , so that the voltage V4 changes from the time t ₃ to the zero point of the current i' ₁ . drops until the crossing point t ₅ . At time _t5 , current _i'1 becomes negative, forward biasing diode BD681 of Darlington transistor Q2 and fixing voltage V4 again to chassis ground potential.

Since sweep switch 27 is shorted during standby mode operation, the voltage developed in winding W2 of the flyback transformer is the same as voltage V4 of FIG. 3d, but with a different AC zero volt reference level. Therefore, during standby operation, the peak-to-peak voltage of winding W2 is, for example, about 25 volts compared to, for example, 900 volts during normal mode operation, and the peak-to-peak voltage decreases to about 3% of that during normal operation. It is.

Since the conduction of the horizontal drive transistor Q5 is prevented by the reverse bias of the diode D8 or D9, the operation of the horizontal oscillator 32 during standby mode operation does not prevent the free running operation of the SICOS type power supply 20.

Standby power for remote control circuit 30 and horizontal oscillator 32 is drawn from winding W _c of horizontal drive transformer T2 as current i ₂ charging capacitors C8 and C4 during standby operation. The average value of the positive portion of current i ₂ shown in FIG. 3f amounts to about 150 mA, corresponding to about 1.8 watts of usable power at the output of the 12 volt regulator. Third
The positive current i ₃ in the winding W _b of the transformer T2 shown in diagram e is induced by the current i ₂ . This current i ₃ has a large amplitude because the number of turns of the winding W _b is only 1/2 that of the winding W _c .
For example, the inductance of the winding W _b is approximately 200 μH, and that of the winding W _c is approximately 800 μH.

Resistors R7 and R8 serve to smooth the base current _i3 . When D2 is cut off, some energy is stored in the winding W _c via resistor R7, stretching the base current i ₃ . Horizontal output transistor Q4 remains safely saturated until the current through its collector is zero.

To return the television receiver to normal operation, a positive pulse ON command signal is applied from the remote control circuit 30 to the base of the switching transistor Q2 via the control line 31 for about 1 second, and then the holding line 26 is applied to the base of the switching transistor Q2. Ensure that a sufficient holding current is obtained from the transistor. The trend generator 21 including the sweep switch 27 is again connected to the switching transistor Q.
2 directly to the chassis ground point 28,
The emitter of horizontal output transistor Q4 is set to ground potential. Therefore, winding W2 of the flyback transformer
The current i' ₁ is passed through the drive transformer T by the transistor Q2.
2 winding W _c is shunted to ground, resulting in a significant decrease in the current i ₂ and the horizontal output transistor Q4.
continues to be unable to remain saturated.

The operation of the SICOS type power supply 20 changes to a series of start-up operations similar to those described in the above-mentioned British published patent specification, in which the retrace ringing causes an increase in the retrace voltage supplied to the primary winding W1 of the flyback transformer T1. The amplitude is controlled until it is high enough to reenergize the SICOS regulator control circuit 22. When the regulator control circuit is re-energized, the interruption of output switch S1 is synchronized with the horizontal retrace while the retrace pulse voltage saturates transistor Q1, causing resistor R1 to
The multivibrator network of R4 and capacitor C2 is deenergized.

During this transition from standby operation to normal operation, the current
What induces the current i ₃ changes from the current in the winding W _c of the drive transformer T2 to the current in the winding W _a , but similarly, during the transition from normal operation to standby operation, the cause that induces the current i _{3 changes from the current in the winding W c of the drive transformer T2} to the current in the winding W a. Winding W _a changes to W _c . In order to safely perform this conversion without damaging the horizontal output transistor Q4,
The switching action of its transistor Q4 is not interrupted during the transition, and it is not made conductive when there is a significant positive voltage V3 on its collector.

During standby, the horizontal oscillator 32 is operating, but when the voltage V4 is low, it is only connected in circuit to the base of the horizontal drive transistor Q5, and the current _1'1 flows in the angular direction from the diode of the Darlington transistor Q2. Therefore, even if a switching signal is applied to the base of the drive transistor Q5 during standby, only a small amount of negative current _i3 flows and does not affect the operation of the transistor Q4.

When the current 1' ₁ becomes positive, the voltage V4 rises, and the collector current of the transistor Q5 flows through the diodes D8,
It is interrupted by D9 and the positive current i ₃ continues to flow and bias transistor Q4 into saturation.

When the television receiver is switched from standby operation to normal operation, transistor Q2 becomes saturated, and immediately after receiving the ON command signal, voltage V _b is zero volts, so current i ₃ driving horizontal output transistor Q4 is zero. Therefore, the SICOS power supply circuit 20 continues to run free like during standby, and the retrace circuits L _H and C _R ring to produce a gradually increasing amplitude voltage V at the retrace frequency during the period t ₁ to _{t 3} in FIG.
Generate 3.

The automatic frequency phase control section of the horizontal oscillator 32
Although not shown in the figure, the phase of the oscillation output begins to match the phase of the ringing voltage V3. This ringing voltage of increasing amplitude occurring in the retrace capacitor C _R is caused by the winding W1 of the flyback transformer
Transistor Tr3 via control winding L1c of 1
is applied to the base of output switch S1 to make that transistor conductive, thereby turning off transistor Tr1 of output switch S1. Therefore, the ringing voltage V3 of increasing amplitude causes the interruption of the switch S1 to the horizontal oscillator 3.
It starts to synchronize with the phase of output 2.

As the voltage V _b rises, the already properly phased oscillator 32 causes the horizontal drive transistor Q5 to
is controlled to supply correctly phased base current _i3 to horizontal output transistor Q4. The ringing voltage of increasing amplitude causes transistor Q1 to conduct, thereby disenergizing the multivibrator circuit of resistors R1-R4 and capacitor C2 while simultaneously energizing regulator control circuit 22.
When regulator control circuit 22 is energized, voltage V3 rises smoothly to its nominal steady-state conduction value.

When switching the television receiver from normal operation to standby operation, this transition is a controlled transition that continuously safely brings horizontal output transistor Q4 into saturation. When receiving the off command signal, the remote control transistor Q2 is cut off and the operation of the horizontal drive transistor Q5 is stopped. If transistor Q2 is suddenly cut off during the retrace period, the current induced from W _a in winding W _b of drive transformer T2 will be higher than the current induced from W _c and the horizontal output transistor Q
4 continues to shut off until the end of retrace and is then maintained at continuous saturation.

The SICOS type power supply 20 operates at the low free-running frequency described in the UK patent specification for the first few milliseconds after the off command signal, but the capacitor C1 in FIG. 1 is sufficiently discharged and the transistor Q1 is cut off. When this happens, the multivibrator circuit of resistors R1-R4 and capacitor C2 is energized, raising the operating frequency of the SICOS switches S1 and S2 to a free-running frequency close to the horizontal deflection frequency, as described above.

The standby circuit configuration of FIG. 1 described above also provides protection against short circuits and overloads. The switching transistor Q2 is controlled only by an on/off command signal supplied from the remote control circuit 30,
When this transistor is turned on, it is kept in saturation by the base current supplied from the holding line 26. If there is a short circuit or overload, the voltage V _b drops below approximately 6.5 volts and the remote control switching transistor Q
2, the television receiver and the SICOS type power supply 20 are operated in a standby mode, and in this standby mode operation, the voltage V _b is completely lowered to prevent the overcurrent condition from continuing. Thus, no matter how many times the television receiver is attempted to return to normal operation, it will normally return to standby mode operation unless the overload operating condition is eliminated.

An example of horizontal drive transformer T2 is as follows.

Magnetic core - cylindrical shape 30 x 6 mm, material N27.

W _a −0.2mm, 350 turns of wire, 4mH.

W _b −0.4mm, 80 turns of wire, 200μH.

W _c −0.2mm, 160 turns of wire, 800μH.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the power supply and deflection circuit of a television receiver having a standby remote control circuit embodying the present invention, FIG. 2 is a diagram showing waveforms of the circuit of FIG. 1 in normal mode operation, and FIG. 1 is a diagram showing waveforms in the standby mode operation of the circuit of FIG. 1, and FIG. 4 is a diagram showing a detailed embodiment of the output circuit of the SICOS type power supply. 20... Switching power supply, 21... Deflection generator, L _H ... Deflection winding, 27... Sweep switch,
32...Oscillation means, Q2...Mode switching means.

Claims (1)

[Claims] 1. Oscillating means; a deflection generator including a deflection winding and a sweep switch; a switching power supply coupled to the deflection generator and supplying power; coupled to the deflection generator; operating the deflection generator and the switching power supply in a normal mode in response to a first command signal, and operating the deflection generator and the switching power supply in a standby mode in response to a second command signal. and; in the normal mode, the sweep switch operates on and off in synchronization with an oscillation signal from the oscillation means to generate a scanning current in the deflection winding to change the deflection. generating a retrace pulse in a generator;
The switching power supply repeatedly turns on and off in response to the retrace pulse, and supplies power in synchronization with the retrace pulse. Also, in the standby mode, the sweep switch operates independently of the operation of the oscillation means. A television display device configured to conduct continuously regardless of the presence of the retrace pulse to cause the switching power supply to self-oscillate regardless of the absence of the retrace pulse.