JPH0339979Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a horizontal deflection output/high voltage generation circuit for a television camera that operates by supplying DC power from the outside.

Conventionally, in the above-mentioned television cameras, no attempt has been made to particularly reduce the peak value of the rush current. In the above-mentioned television camera, for safety reasons, the capacity of the fuse inserted into the power line is set to a fuse with a capacity that is approximately twice the current consumption value during normal operation to prevent the fuse from blowing out due to rush current. are used, and are inferior in terms of safety. Furthermore, in the case where power is supplied from a battery, the large peak value of the above-mentioned rush current shortens the usable time of the battery.

The present invention was developed to solve the above-mentioned problems in the conventional technology, and it improves safety by reducing the difference between the blowing current value of the fuse used and the operating current value in the normal operating state of the circuit, and The power is turned on and off repeatedly,
Moreover, it is an object of the present invention to provide a horizontal deflection output/high voltage generation circuit for a television camera, which prevents shortening of the operating time of the battery when the battery is used.

An embodiment of the horizontal deflection output/high voltage generation circuit for a television camera according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram of a power supply system to a television camera according to the present invention. In the figure, 1 refers to the entire television camera, 2 is an input connector that accepts power supplied from an external DC power supply or battery to the television camera 1, and 3 is a device that accepts external power input from the input connector 2. This is a constant voltage circuit for adjusting the voltage to the required voltage and stabilizing the voltage. Reference numeral 4 designates other circuits other than the synchronizing signal generating circuit, the signal system amplifier, and the horizontal deflection output/high voltage generating circuit, which are operated by being supplied with the required constant voltage from the constant voltage circuit 3 after the power is turned on. 5 is a horizontal deflection output/high voltage generation circuit for generating a horizontal deflection output of the image pickup tube and a high voltage for each electrode. The horizontal deflection output
The operation of the high voltage generating circuit 5 is controlled by the control circuit 6 so that it operates later than the operations of the other circuits 4 described above only when the power is turned on. That is,
As can be understood from the explanation of the power supply system diagram above, in the present invention, the operation of the horizontal deflection output/high voltage generation circuit 5 is controlled by the control circuit 6 only when the power is turned on, and the operation of the other circuits 4 is controlled by the control circuit 6. The configuration is such that the peak value of the rush current is reduced by delaying the delay.

FIG. 2 is an actual circuit diagram showing an embodiment of the horizontal deflection output/high voltage generation circuit according to the present invention.

In FIG. 2, Q1 is a gate transistor constituting the above-mentioned control circuit 6, and the emitter of the gate transistor Q1 is connected to the power supply line +B.
(connected to the constant voltage circuit 3 described above), and the capacitor C1 is connected between the base and the emitter.
However, a resistor R1 is interposed between the base and ground, and the collector of the gate transistor Q1 is connected to the emitter of the horizontal drive transistor Q2 via a resistor R3. A horizontal drive signal (HD) is supplied from the terminal T to the base of the horizontal drive transistor Q2 through the coupling resistor R2, and its output is taken out from the emitter and then passed through the horizontal output transistor Q3 via the coupling capacitor C2. supplied to the base of Note that the diode D1 interposed between the base of the horizontal output transistor Q3 and the ground is a clamp diode. Further, a horizontal deflection coil Ly is connected in parallel between the collector and emitter of the horizontal output transistor Q3, a capacitor C3 is connected in parallel to the horizontal deflection coil Ly, and the collector of the horizontal output transistor Q3 is connected in parallel. Connected to the primary winding of the back transformer FBT. Note that D2 is a damper diode. The damper diode D2 is a switch element that, together with the horizontal output transistor Q3, switches the deflection current supplied to the horizontal deflection coil Ly during the scanning period and retrace period, and as is well known, when the horizontal output transistor Q3 is turned on, In some cases, a deflection current is supplied to the horizontal deflection coil Ly via the horizontal output transistor Q3,
Further, when the horizontal output transistor Q3 is in an off state, a deflection current is supplied to the horizontal deflection coil Ly via the damper diode D2.

Therefore, the operation of the circuit consisting of the above configuration is as follows.
This will be explained with reference to FIG. As shown in the figure, the horizontal drive signal (HD) supplied to the base of the horizontal drive transistor Q2 is set such that V _L >0 at a low level and V _H <+B at a high level.

First, we will explain the operation immediately after the power is turned on. Immediately after the power is turned on, the base voltage of the gate transistor Q1 is approximately +B of the supply voltage.
, and the gate transistor Q1 is in an off state. 1 in FIG. 3 shows the change in the base voltage of the gate transistor Q1 with respect to time. The horizontal axis shows time t, and the vertical axis shows base voltage V _B. The characteristic curve shown by the solid line is the time constant of capacitor C1 and resistor R1 (C1×
This is the curve determined by R1). Now is the time
If the power is turned on at time _t1 , the base voltage of the gate transistor Q1 is approximately +B of the supply voltage, as described above, and at this time the gate transistor Q1 is in an off state. and,
As time passes, charge is accumulated in the capacitor C1 through the resistor R1, and the capacitor C1
As charging progresses, the base voltage of the gate transistor Q1 decreases, and at time _t2 , when the base to emitter of the gate transistor Q1 becomes forward biased (V _BE1 ), the gate transistor Q1
is in the on state. That is, t ₁ when the power is turned on
From the point of time, the base of gate transistor Q1 ~
The gate transistor Q1 is in the OFF state until time t ₂ when the emitter is forward biased (V _BE1 ), but after the above-mentioned time t ₂ , the gate transistor Q1 is forward biased and is in the ON state. Become.

As described above, immediately after the power is turned on, the base of the gate transistor Q1 is approximately at +B of the supply voltage, and at this point, the gate transistor Q1 is in an off state. Therefore, the horizontal drive transistor Q2 is also in an off state, and no current flows through the horizontal drive transistor Q2, and the horizontal drive signal (HD) supplied to the base at this time is transmitted to the horizontal output transistor Q2.
3 will not be supplied to the base. Further, while the gate transistor Q1 is in the off state, the base of the horizontal output transistor Q3 is clamped to the ground potential by the clamping diode D1, and the horizontal output transistor Q3 is clamped to the ground potential by the clamping diode D1.
is also in the off state.

Subsequently, as time passes, charge is accumulated in the capacitor C1 through the resistor R1, and the base voltage of the gate transistor Q1 decreases, resulting in forward bias (V _BE1 ) between the base and emitter of the gate transistor Q1. At the above-mentioned time point _t2 , the gate transistor Q1 is turned on. The above-mentioned gate transistor Q1
Based on the on state at time _t2 , the horizontal drive transistor Q2 is turned on, and the horizontal drive signal (HD) supplied to the base of the horizontal drive transistor Q2 is taken out from its emitter and transferred to the coupling capacitor C2. It is supplied to the base of the horizontal output transistor Q3 via. Figure 3 2
is the emitter voltage waveform of the horizontal drive transistor Q2. In addition, FIG. 3 shows the base voltage waveform of the horizontal output transistor Q3, and V _FD1 in the figure is the forward voltage of the clamping diode D1. The charge of C2 flows through the horizontal drive transistor Q2 to the clamping diode D1, and the base of the horizontal output transistor Q3 is clamped to V _FD1 . That is, the low level V _L of the horizontal drive signal (HD) is clamped approximately to the emitter potential of the horizontal output transistor Q3. When the horizontal drive signal as shown in FIG. 3 is supplied to the base of the horizontal output transistor Q3, the horizontal output transistor Q3 is turned off during the negative pulse portion and is turned on during the rest of the period. Become. Therefore, by using an inductance as the load and connecting the damper diode D2 as shown in FIG. 2, a sawtooth current flows through the horizontal deflection coil Ly as in the well-known deflection method. By making the load of the horizontal output transistor Q3 in the form of a flyback transformer as in the embodiment shown in Fig. 2, each electrode voltage required by the image pickup tube can be supplied from the secondary side of the flyback transformer FBT. high voltage can be extracted.

Note that if a transistor is interposed in series between the power source and the load, and the operation of the transistor is delayed from the switch operation, and the power is applied to the load with a delay from the switch operation, the load current will flow directly through the transistor. Therefore, a transistor with a large current capacity is required (several hundred milliamps).
The gate transistor Q1 in the present application constitutes the control circuit 6, and since the horizontal drive signal (HD), which is a load, does not flow therethrough, a transistor with a small current capacity is sufficient regardless of the load.

As described above, according to the present invention, although the horizontal deflection power and each electrode voltage in a television camera occupy a relatively large amount of power, the operation of the horizontal deflection output/high voltage generation circuit is more efficient than the operation of other circuits other than this. By delaying the operation, it is possible to provide a horizontal deflection output/high voltage generation circuit for a television camera that can significantly reduce the peak value of rush current when the power is turned on.

In addition, in the above-mentioned television camera, a fuse is generally inserted in the power supply line in case of an abnormal situation. However, the value of the fuse is not determined by the operating current value of the circuit, but is often restricted by the peak value of the rush current, which poses a problem in terms of ensuring safety. According to the present invention described above, the fuse blowing value can be brought close to the actual operating current value,
Furthermore, in portable cameras that operate on battery power, the power is often turned on and off, but suppressing the rush current means that the battery can be used for a longer period of time, and a simple circuit configuration is required. This provides greater practical effects.

[Brief explanation of the drawing]

Figure 1 is a power supply system diagram of the circuit according to the present invention.
FIG. 2 is a circuit diagram showing an embodiment of the horizontal deflection output/high voltage generation circuit according to the present invention, and FIG. 3 is a waveform diagram for explaining the above-mentioned embodiment according to the present invention. Q1...Gate transistor, Q2...Horizontal drive transistor, Q3...Horizontal output transistor, D1...Clamp diode, D
2...damper diode, Ly...horizontal deflection coil, C1...capacitor, B1...resistance.

Claims (1)

[Scope of utility model registration request] In a television camera that operates by receiving DC power from an external source, after the power is turned on, a part of the operating power supply voltage of the circuit is stored in a capacitor through a resistor, and the terminal voltage of the capacitor is set to an arbitrary constant value. is interposed between the gate transistor and the base of the horizontal output transistor to start supplying the horizontal drive signal to the horizontal deflection output section when the voltage exceeds the horizontal output transistor. The operation of the horizontal deflection output/high voltage generation circuit, which is equipped with a clamping diode for clamping and generates a horizontal deflection output of the image pickup tube and a voltage for each electrode of the image pickup tube after the power is turned on, is controlled by the horizontal deflection output/high voltage generation circuit. Horizontal deflection output of a television camera, which is characterized by operating later than the operation of other circuits except for the high voltage generation circuit.
High voltage generation circuit.