JPS5836543B2 - Output circuit protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device for an output circuit in a device that controls the output power of an output circuit by controlling the pulse width of a drive pulse applied to an output circuit such as a horizontal output circuit. It is an object of the present invention to provide a device capable of preventing and protecting against excessive input at the time of power-on and at the time of overvoltage and overcurrent.

In the horizontal deflection circuit, the phase and power of the deflection and low-voltage power supply outputs change depending on the temperature change of the deflection yoke and the content of the brightness signal, so control is performed to compensate for these fluctuations by some means. However, as a way to facilitate such compensation, a method has been proposed in which the phase and pulse width of the drive pulse of the horizontal output transistor are automatically adjusted based on the horizontal deflection phase shift and output detection output.

First, this type of apparatus will be explained with reference to FIGS. 1 and 2.

In Fig. 1, 1 is a triangular wave generation circuit that creates a triangular wave synchronized with a horizontal synchronization signal, 2 is a horizontal output circuit, and 3 is a circuit that generates a horizontal periodic pulse for horizontal drive (hereinafter referred to as a drive pulse) based on the triangular wave. A phase control circuit 4 adjusts the phase so as to automatically compensate for the shift in the deflection phase in the horizontal deflection output circuit 2; A pulse width controller 5 amplifies the phase and pulse width adjusted drive pulse to automatically compensate the magnitude of input power to the horizontal output circuit 2; This is a drive circuit that supplies

Next, the detailed configuration and operation of each part will be explained.

First, in the triangular wave generation circuit 1, 6 is a charging/discharging capacitor for generating a triangular wave, and 7 is this capacitor 6.
8 is a charge/discharge control circuit that switches between charging and discharging the capacitor 6 and controls the magnitude of the current during charging and discharging; 9 is a voltage at the capacitor 6; A voltage detection circuit detects the value and generates a switching signal for charge/discharge switching of the charge/discharge control circuit 8; 10 is a comparison signal generation circuit that generates a comparison signal for synchronization control; 11 is a horizontal synchronization signal input terminal 12 13 is a phase comparison circuit that compares the phase of the horizontal synchronization signal and the comparison signal; 14 is a phase comparison circuit that smoothes the comparison output of the phase comparison circuit 13 and controls the charging/discharging control circuit 8 for charging/discharging. This is a filter that is applied as a current control signal.

With this configuration, if the charge/discharge control circuit 8 is now switched to charge the capacitor 6, the capacitor 6 will be charged with a constant current and its terminal voltage will be as shown in FIG. 2B. It rises linearly as shown.

It is assumed that during this rising period, the output signal of the voltage detection circuit 9 is at a high level as shown in FIG.

When the terminal voltage of the capacitor 6 rises and reaches a predetermined high voltage BH, the voltage detection circuit 9 detects this and inverts its output signal C to a low level. Switch to discharge at constant current.

Therefore, the terminal voltage B of the capacitor 6 now falls linearly.

The terminal voltage B of the capacitor 6 decreases to a predetermined low voltage BL.
When this occurs, the voltage detection circuit 9 detects this and inverts the output signal C to a high level again, and the charge/discharge control circuit 8
Switch to charging state.

By repeating this process, a triangular wave as shown in FIG. 2B can be obtained at the capacitor 6.

On the other hand, in the comparison signal generation circuit 10, the capacitor 6
Based on the triangular wave B and the switching output signal from the voltage detection circuit 9, comparison signals located in the first and second half of the falling part of the triangular wave B, respectively, are generated as shown in FIG. 2 DI+D2.

Then, in the phase comparator circuit 13, this comparison signal D1,
D2 and a horizontal synchronizing signal as shown in FIG. 2A shaped by the waveform shaping circuit 11 are compared to generate a comparison output signal as shown in FIG. 2E.

When this comparison output signal E is smoothed with a filter, as shown in the figure, when the center of the falling part of the triangular wave B is synchronized with the horizontal synchronizing signal, it is n O n, and when it is not, the phase is advanced. or “correct” depending on the delay
Alternatively, a control signal that becomes negative can be obtained, and this is fed back to the charge/discharge control circuit 8 to control the magnitude of the charging current and discharging current of the capacitor 6, thereby changing the phase of the triangular wave B to the horizontal synchronizing signal A. Synchronize with.

In this way, the triangular wave generating circuit 1 generates the horizontal synchronizing signal A.
A triangular wave B synchronized with is generated.

Next, the phase control circuit 3 and pulse width control circuit 4 create a horizontal drive pulse based on this triangular wave B, and adjust its phase and pulse width.

First, in the phase control circuit 3, the phase comparator circuit 15 generates a triangular wave
A comparison signal is generated based on the signal, and the phase of this signal is compared with a flyback pulse as shown in FIG. .

This detection signal is added as a phase control signal, and it controls the phase of the drive pulse as shown in Figure 2 G, which is created based on the triangular wave B, so that even if there are changes in the operation of the deflection circuit due to temperature changes, etc., the drive pulse remains level. Control to maintain correct deflection phase.

It goes without saying that the phase of this drive pulse G is advanced by a time width t, which is delayed by the influence of the accumulation time of the horizontal output transistor, and for this reason, the comparison signal output of the phase comparator circuit 15 is also set in this phase. The phase is set to advance by a time width t8.

After controlling the phase correctly in this way, the pulse width control circuit 4 further controls the width of the drive pulse using a detection signal of a magnitude corresponding to the magnitude of the deflection output taken out from the horizontal deflection output circuit 2, and deflects the drive pulse. A drive pulse G controlled to keep the output constant is generated.

In the illustrated device, since the trailing edge of the drive pulse G is determined by the phase control circuit 3 at the reference phase with respect to the flyback pulse F, it is not possible to adjust the pulse width by changing this. The pulse width is controlled by changing the edges.

The drive pulse G whose pulse width has been adjusted in this manner is amplified by the drive circuit 5 and then applied to the horizontal deflection output circuit 2.

This horizontal deflection output circuit 2 includes a horizontal output transistor 17, a transformer 18, three diodes 19 to 21, a horizontal deflection coil 22, an S-shaped correction capacitor 23, a resistor 24, 25 for detecting voltage, and a capacitor 26. , a flyback transformer 27, a diode 28 for high-voltage rectification, a resistor 29 for taking out the ABL voltage, a capacitor 30, and a diode 31 for supplying low-voltage power. 32.

When a drive pulse G whose pulse width is appropriately adjusted is supplied to such a horizontal output circuit 2, the damper diode 21 causes the horizontal deflection coil 22 to be
The horizontal output transistor 17 is made conductive during a later part of the period tj during which the deflection current is flowing during the period ti, so that its collector current becomes as shown in FIG. 2H, and during this period t
It is possible to store energy in the transformer 18 by passing current through the transformer 18 for an extra period of j, and by controlling the amount of stored energy by the pulse width of the drive pulse G, the deflection output can be kept constant. , is a well-known circuit.

The phase control circuit 3 and pulse width control circuit 4 will be explained in further detail.

In this device, a switching pulse generating circuit 33 is provided to switch and operate the two control circuits 3 and 4 for controlling the phase and pulse width of the drive pulse, and here, based on the triangular wave B, as shown in FIG. Two switching signals having mutually opposite polarities such as I and I, whose polarities are reversed during the voltage rising period and during the voltage falling period of the triangular wave B, are generated.

This circuit may be constructed by, for example, a differential circuit that detects a change in the slope of the voltage change of the triangular wave B, and a flip-flop that is inverted by the differential output.

The phase control circuit 3 is composed of a differential amplifier consisting of transistors 34 to 3γ, and the pulse width control circuit 4 is composed of a differential amplifier composed of transistors 34 to 3γ.
It is constituted by a differential amplifier consisting of transistors 8 to 41, and also includes a transistor 42 for output and transistors 43 and 44 connected to a common emitter for operation switching.

The output transistor 42 outputs a high-level drive pulse G from its collector only when both the transistors 36 and 39 are in a cutoff state and the transistors 35 and 40 are both in a conductive state.

The triangular wave B from the triangular wave generating circuit 1 is passed through the emitter follower transistor 45 to the transistors 37 and 3.
8, the switching signal ■ from the switching signal generating circuit 33 is applied to the base of the transistor 44, and the switching signal ■ is applied to the base of the transistor 43, and the switching signal ■ from the switching signal generating circuit 33 is applied to the base of the transistor 43.
The phase comparison signal ψ from the horizontal output circuit 2 and the filter 16 is applied to the base of the transistor 34, and the output voltage detection signal δ from the horizontal output circuit 2 is applied to the base of the transistor 41.

First, assume that it is now period T1, and the switching signal (2) from the switching signal generating circuit 33 is at a high level and the switching signal (2) is at a low level.

At this time, the transistor 44 becomes conductive.
3 is cut off, and only the phase control circuit 3 is switched to the operating state.

During this period T1, as is clear from FIG. 3, the voltage of the triangular wave B gradually decreases.

Therefore, if the magnitude of the phase comparison signal φ from the phase comparator circuit 15 and the filter 16 is set to be at a level midway through the triangular wave B, the magnitude of the triangular wave B will be lower than the phase in the first half of this period T1. During the period T1a, which is greater than the magnitude of the comparison signal ψ, the transistors 36, 37 are conductive with their collectors at a low level, and the transistors 34, 34, 37 are conductive.
35 is shut off and its collector is at a high level, so
The transistor 42 is not conductive and the drive pulse G output is at a high level.

Then, when the magnitudes of the two are reversed and the magnitude of the triangular wave B becomes smaller than the magnitude of the phase comparison signal φ, this period T
In the later period Tlb of 0, the transistor 36 . 37
transistors 42 and 35 are turned on and their collectors are turned low so that transistors 34 and 35 are turned on and their collectors are low.
becomes conductive, so the drive pulse G continues for a period T after this point.
, b is inverted to a low level.

In this state, when the period T1 in which the switching signal ■ is at a high level ends and the next period T2 when the switching signal ■ is at a low level and the switching signal ■ is at a high level, the transistor 44 is cut off and the transistor 43 is turned on. The state is reversed, and only the pulse width control circuit 4 is switched to the operating state.

Then, during this period T2, the voltage of the triangular wave B gradually increases.

Therefore, if the magnitude of the output voltage detection signal δ from the horizontal output circuit 2 is set to a level halfway between the triangular wave B, the magnitude of the output voltage detection signal δ will be set to the level of the triangular wave B in the first half of this period T2. During the period T1b, which is larger than the width of (1), the transistor 40 and 41 are conductive and their collectors are at a low level, and the transistors 38 and 39 are cut off and their collectors are at a high level, so the transistor 42 is in a period T1b. Then, the conduction state continues and the drive pulse G
remains at a low level.

Next, when the magnitudes of the two are reversed and the magnitude of the output voltage detection signal δ becomes larger than the magnitude of the triangular wave B, the transistor 40.
41 is cut off and its collector becomes high level, and transistors 38 and 39 are made conductive and their collector becomes low level, so transistor 42 is cut off and the drive pulse G is applied during this period. Invert T2a to high level again.

When the low level period T2 of the switching signal (2) ends in this state, the state returns to the first period T, and the above-described operation is repeated thereafter.

As is clear from the above explanation, the trailing edge of the drive pulse G determines the phase of the horizontal deflection operation, so the phase of the flyback pulse F extracted from the horizontal output circuit 2 and the phase of the triangular wave B are The phase comparator circuit 15 calculates the difference between
The phase of the drive pulse G can be automatically controlled by controlling the comparison level with the triangular wave B to be changed based on the detection signal ψ detected by the filter 16.

Furthermore, the position of the leading edge of the drive pulse G determines the period during which the collector current (hatched portion) of the collector current H of the horizontal output transistor 17 flows before the start of horizontal deflection (shaded area), thereby determining the magnitude of the horizontal output. Therefore, horizontal output circuit 2
By controlling the comparison level with the triangular wave B to be changed using the horizontal output detection signal δ extracted from the horizontal output detection signal δ, it is possible to automatically control the pulse width of the drive pulse G so that the horizontal deflection output is always constant. It is something that

In this manner, the output power of the horizontal output circuit 2 is stabilized in this device, but there is a risk that the horizontal output circuit 2 will be overloaded and destroyed when the power is turned on.

In other words, when the power is turned on, even if sufficient power is supplied to the horizontal output circuit 2, the output power will not rise immediately, so the pulse width control circuit 4 will widen the pulse width and output power until then. In this case, a control voltage is applied that increases the voltage, a drive pulse with a wide pulse width is applied, and an excessive input power is applied.

In addition to such horizontal deflection devices, similar problems have widely occurred in devices that control the pulse width of drive pulses, such as switching regulator-type power supply stabilization circuits.

Therefore, the present invention eliminates such conventional drawbacks, and prevents the output circuit from being destroyed even when the power is turned on.
The purpose is to provide a device that can protect against overvoltage, and uses a bistable circuit and an integrating circuit to gradually increase the output power of the output circuit when the power is turned on and when operation starts after a temporary stop. The present invention is characterized in that the pulse width control circuit is controlled by the output of the bistable circuit, and the capacitor is charged by the output of the bistable circuit, and the supply of the drive pulse is stopped when a certain value is exceeded.

Hereinafter, a first embodiment of the present invention implemented in a horizontal deflection device will be described with reference to FIG. 4.

In FIG. 4, the same parts as in the prior art are designated by the same reference numerals as in FIG. 1, and the explanation thereof will be omitted.

In FIG. 4, 46 is an operation start control circuit newly provided for this purpose, which includes a bistable circuit 47 and an integrating circuit 48.
, a reset resistor 49 , a discharge circuit 50 , and a voltage fixing circuit 51 .

The bistable circuit 47 consists of a transistor 52.53.
It consists of a stable multi-by-break (flip-flop), and in this bistable circuit 47, when the power is turned on, the base potential of transistor 53 is always higher than transistor 5.
The base potential of transistor 5 becomes lower than the base potential of transistor 5.
In the first state, the transistor 53 is turned on and the transistor 53 is turned off.

Therefore, at this time, the collector output of transistor 52 becomes low level, and transistor 54 in integrating circuit 48 becomes conductive.

The naran resistor 54 is configured to function as a constant current source circuit, and the transistor 54, the resistor 55, and the capacitor 56 constitute an integrating circuit.

When the transistor 54 is conductive, a constant current flows into the capacitor 56 through it, and is integrated to gradually increase the voltage at its terminal, which is inverted by the transistor 57 to provide a gradually decreasing output voltage.

The output voltage taken out from the collector of the transistor 57 is applied to the base of the transistor 58 provided in parallel with the transistor 41 in the pulse width control circuit 4, and also to the horizontal output circuit 2,
The pulse width of the drive pulse G for driving is controlled.

At this time, the integrating circuit 4 taken out from the transistor 57
The pulse width of the drive pulse G is controlled to be smaller as the output voltage of 8 becomes larger.

Therefore, since the output voltage of the integrating circuit 48 is high immediately after power is turned on, the pulse width of the drive pulse G is controlled to be small, and the input power to the horizontal output circuit 2 is small.

As the output voltage of the integrating circuit 48 gradually decreases over time, the pulse width of the drive pulse G is also controlled to gradually increase, and a gradually larger input power is supplied to the horizontal output circuit 2.

As a result, when the power is turned on, large input power is suddenly supplied to the horizontal output circuit 2 and excessive output power is not output, and the horizontal output circuit 2 gradually returns to the normal operating state as the input power gradually increases. As a result, there is no risk of destruction due to excessive output.

After a certain period of time has passed in the integrating circuit 48, the capacitor 56
When the terminal voltage increases and the output voltage of the integrating circuit 48 reaches a predetermined voltage, the base potential of the transistor 53 of the bistable circuit 47 is increased via the reset resistor 49 provided at the emitter of the transistor 57. , transistor 5
3 conducts, transistor 52 is cut off, and the transistor 52 is inverted to the second state.

The timing of this inversion is such that the output voltage applied from the collector of the transistor 57 to the base of the transistor 58 is applied from the horizontal output circuit 2 to the transistor 4 in a steady state.
The timing may be set such that the pulse width control voltage becomes smaller than the control voltage applied at 1 and the pulse width control is thereafter performed in a steady state.

Of course, it goes without saying that the time should be set so that the horizontal output circuit 2 is in a steady operating state by the time of this inversion.

This time can be set by arbitrarily determining an integral time constant.

When the bistable circuit 47 is inverted to the second state, the collector output of the transistor 52 becomes high level, which turns on the transistor 59 and discharges the capacitor 56 in the integrating circuit 48 at high speed.

By discharging the integrating circuit 48 at a high speed in this way, even if the power is immediately turned off and then turned on again, the above-mentioned protective operation can be started immediately, and the horizontal output can be prevented by mistake. The risk of destroying the circuit 2 can be eliminated.

At this time, the output of the collector of the transistor 52 in the second state of the bistable circuit 47 makes the transistor 60 in the voltage fixing circuit 51 conductive, and the voltage applied to the transistor 58 of the pulse width control circuit 4 is set to a sufficiently small value. It would be more convenient if the pulse width control by the detection voltage from the horizontal output circuit 2 was not affected by fixing the voltage to .

Furthermore, a resistor 61 is connected to the secondary winding of the flyback transformer.
, 62, the detection voltage that changes in the negative direction at the time of overvoltage output or overcurrent output is taken out, and when the detection voltage exceeds a predetermined value in the detection circuit 6, the transistor 64 is cut off and the drive in the horizontal drive circuit 5 is Transistor 6 as a switching element provided in the pulse supply path
5 is made conductive, thereby temporarily stopping the supply of drive pulses for protection.

At the same time, the transistor 66 is switched and the transistor 67 in the bistable circuit 47 is cut off to put the bistable circuit 47 into the first state.

Therefore, in this case, even when the operation is restarted to start supplying drive pulses to the horizontal output circuit 2 again, a gradually larger input power is supplied to the horizontal output circuit 2.

This prevents the horizontal output circuit 2 from suddenly receiving large input power and outputting excessive output power when restarting operation, and the horizontal output circuit 2 gradually returns to normal operation as the input power gradually increases. As a result, there is no risk of destruction due to excessive output.

Furthermore, since such excessive current or voltage is repeatedly output, the operation stop control circuit 6 is required to completely stop the operation in such cases.
It is 8.

Here, each time the bistable circuit 47 enters the first state, the transistor 69 acting as a constant current source is made conductive to charge the capacitor 70, and the overvoltage and overcurrent outputs are repeated and the charging voltage increases. When a predetermined voltage determined by resistors 71 and 72 is exceeded, it is detected by a switching circuit using a differential amplifier configured with transistors 73 and 74, and the output thereof turns on transistor 65 in horizontal drive circuit 5 to generate a drive pulse. supply will be completely stopped.

Furthermore, even more complete protection can be achieved by keeping the transistor 65 conductive with this detection output for self-holding, thereby stopping the operation until the operator turns off the power supply.

In this way, with this device, excessive input power is not applied to the horizontal output circuit 2 even immediately after power is turned on or operation is restarted, and even when the horizontal output circuit 2 outputs an overcurrent or overvoltage. It is possible to prevent this and eliminate the risk of destruction.

It goes without saying that the bistable circuit 47 may be configured with a known bistable circuit, such as using a self-holding type electromagnetic relay or a silicon-controlled rectifier, in addition to the bistable multi-bibreak described above. do not have.

Furthermore, if a constant current source and a capacitor are used as the integrator circuit 48 as described above, the control time can be made accurate and the change in output voltage can be made linear. An integration circuit including only a resistor, a capacitor, etc. may be used, and its operation may be controlled by a switching element.

Furthermore, the means for controlling the pulse width of the drive pulse may also be arbitrarily adopted other than the above-mentioned embodiments.

Furthermore, although the above embodiments have been described for protecting the output circuit in a horizontal output device, the present invention is also applicable to a wide range of applications in which the output power of the output circuit is controlled by changing the pulse width of the drive pulse. Needless to say, it can be implemented.

As detailed above, the output circuit protection device of the present invention includes a drive pulse generation circuit that generates drive pulses with a constant cycle, an output circuit that is driven by the drive pulses, and a drive pulse generator that changes the pulse width of the drive pulses. and a pulse width control circuit that controls the output power of the output circuit, and a bistable circuit such as a multi-by-break that is put into the first state when the power is turned on or when an overvoltage or overcurrent is output from the output circuit; An integrator circuit that is brought into a charged state by the output in a first state of the circuit and generates an output voltage that changes over time, and a bistable circuit that is activated when the output voltage of this integrator circuit reaches a predetermined voltage. A reset circuit that inverts the bistable circuit to the second state, a discharge circuit that discharges the integrating circuit at high speed by the output of the bistable circuit in the second state, and a discharge circuit that charges the bistable circuit each time it enters the first state. It is equipped with a capacitor and a switching circuit that switches when the charging voltage of this capacitor reaches a predetermined value.The pulse width control circuit is controlled by the output voltage that changes over time generated by the integrating circuit, and the output voltage is output at the start of operation. It is characterized in that the pulse width of the drive pulse is changed so as to gradually increase the output power of the circuit, and the supply of the drive pulse is stopped by a switching circuit when the circuit is in operation.

Therefore, according to the present invention, the output power of the output circuit can be gradually increased by forcibly controlling the pulse width of the drive pulse when the power is turned on and when an excessive output is generated. A device that can prevent damage to the output circuit due to power output, and can also stop the supply of drive pulses to the output circuit when excessive output is repeated, ensuring complete protection. It is.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional horizontal deflection device, Figure 2A
,B,C,D,,D2,E,F,G,H and Figure 3B
, I, ■, F, G, H are waveform diagrams for explaining the operation of the device, and FIG. 4 is a circuit diagram of a horizontal deflection device using an output circuit protection device in an embodiment of the present invention. . 1... Triangular wave generation circuit, 2... Horizontal output circuit, 3... Phase control circuit, 4...
Pulse width control circuit, 5...horizontal drive circuit,
46...Operation start control circuit, 41...
Bistable circuit, 48...Integrator circuit, 49...
...Reset resistor, 50...Discharge circuit, 5
2, 53...Flip-flop naranjistor, 54... Constant current circuit transistor, 56...
... Capacitor, 61, 62 ... Resistor, path, 68 ... Operation stop control circuit. 63...Detection times

Claims (1)

[Claims] 1. A dry Hals generation circuit that generates a drive pulse of a constant period, an output circuit driven by the drive pulse, and a pulse width of the drive pulse that is changed to control the output power of the output circuit. a bistable circuit, such as a multi-by-break, which is set to a first state when the power is turned on or when an overvoltage or overcurrent is output from the output circuit; an integrator circuit that is brought into a charged state by an output and generates an output voltage that changes over time, and inverts the bistable circuit to a second state when the output voltage of the integrator circuit reaches a predetermined voltage. a reset circuit, a discharge circuit that discharges the integrating circuit at high speed by the output of the bistable circuit in the second state, a capacitor that is charged each time the bistable circuit enters the first state, and this capacitor. a switching circuit that is switched when the charging voltage of the integrator reaches a predetermined value; A protection device for an output circuit, characterized in that the pulse width of the drive pulse is changed so as to gradually increase the output power of the output circuit, and the switching circuit stops supplying the drive pulse when the switching circuit is in operation. 2. The output circuit protection device according to claim 1, wherein a flip-flop is used as the bistable circuit. 3. The output circuit protection device according to claim 1 or 2, characterized in that a series circuit of a constant current source circuit and a capacitor is used as the integrating circuit. 4. The output circuit protection device according to claim 1, 2, or 3, wherein a self-holding type switching circuit is used as the switching circuit. 5. The output circuit protection device according to claim 1, 2, 3, or 4, which uses a horizontal output circuit as the output circuit and controls the pulse width of the horizontal drive pulse. . 6. Claims 1 and 2, characterized in that a switching regulator-type power supply stabilization circuit is used as the output circuit, and the pulse width of the drive pulse is controlled.
4. A protection device for an output circuit according to item 3, item 4, or item 4.