JP2666294B2 - Deflection yoke drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection yoke driving circuit mainly provided in a vector scanning type display device. 2. Description of the Related Art Display devices mounted on airplanes and the like often adopt a vector scanning method at present,
As the amount of display information to be transmitted to a pilot or the like increases, a high-speed deflection yoke drive circuit is required. A conventional example of such a deflection yoke drive circuit will be described with reference to FIG. Here, a deflection current 43 is supplied from an amplifier 40 to a deflection yoke 50 based on a deflection signal 42 introduced from a symbol generator (not shown), and a deflection current actually flowing to stabilize the deflection current 43 is provided.
A configuration was adopted in which the feedback resistance 41 was used as a negative feedback for the reference 43. However, in the above conventional method, in order to control the deflection current 43 at high speed, the power supply voltage supplied from the amplifier 40 is opposed to the back electromotive force Ldi / dt generated in the deflection yoke 50. The voltage must be as high as possible, resulting in the problem of increased power consumption. In addition, since a condition of withstand voltage is added, there is a disadvantage that the circuit configuration is complicated. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a deflection yoke drive circuit improved so that both high-speed control of deflection current and power consumption can be improved. Means for Solving the Problems In order to solve the above problems, a deflection yoke drive circuit according to the present invention detects a magnitude of a current flowing through a deflection yoke, and detects a current command value given by an input deflection signal and a current command value. A deflection current control circuit that generates a current corresponding to a deviation from the detection result and outputs the current to the deflection yoke; and an offset current output that generates an offset current corresponding to an offset value indicating the level of the deflection signal and outputs the current to the deflection yoke. And a circuit. The current obtained by adding the offset current that changes according to the level of the deflection signal generated by the offset current output circuit and the current generated by the deflection current control circuit flows through the deflection yoke. The current flowing in the deflection yoke is subjected to negative feedback control by the deflection current control circuit so as to always match the current command value given by the deflection signal. Hereinafter, an embodiment of a deflection yoke drive circuit according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram of the deflection yoke drive circuit, and FIG. 2 is a timing chart of main signals for explaining the operation. A vector scanning type display device mounted on an aircraft is a device that displays information necessary for operation to a pilot as a symbol based on a command from a host computer (not shown). More specifically, it is the symbol generator 1 that is a computer that generates the outline of the symbol or the like in response to the above-mentioned instruction.
The main signal necessary for displaying this symbol on a CRT (not shown) is emitted. Such a deflection yoke drive circuit is provided for controlling a deflection current flowing through a deflection yoke of a CRT in response to a deflection signal which is one of these signals. In addition,
Deflection signals having two types of signals of the X axis and the Y axis are respectively introduced into this deflection yoke drive circuit.
Since both circuit configurations are the same, the deflection yoke drive circuit for the Y axis will be described below. The deflection yoke driving circuit into which the deflection signal 101 from the symbol generator 1 is introduced is a circuit for controlling the deflection current 31 flowing through the deflection yoke 30, and the current source for the deflection current 31 is shared by two circuits. That is, a deflection current 31 obtained by adding a control current 221 from the deflection current control circuit 20 and an offset current 121 from the offset current output circuit 10 is supplied to the deflection yoke 30. First, the offset current output circuit 10 will be described. An offset current output circuit 10 including a D / A converter 11 and an amplifier 12 converts a deflection signal 101 having a predetermined number of bits into a D / A signal.
The converter 11 sequentially converts the analog signal into an analog signal.
1 is converted into a current by the amplifier 12, the offset current 121 is given to the deflection yoke 30 and a feedback resistor 23 to be described later via the resistor 13, and a negative feedback is added to stabilize the offset current 121. I have. Note that the D / A converter 11 does not convert all the bits of the deflection signal 101, and the offset current 121 has a magnitude corresponding to the offset of the deflection signal 101. .
However, the supply voltage of the amplifier 12 is ± V1. Next, a deflection current control circuit 20 including a D / A converter 21 and an amplifier 22 sequentially converts the deflection signal 101 into an analog signal by the D / A converter 21, and converts the converted control signal 211 into a current signal by the amplifier 22. Then, the control current 221 obtained by the current conversion is caused to flow to the ground via the deflection yoke 30 and the feedback resistor 23. Further, since a voltage corresponding to the magnitude of the deflection current 31 including the offset current 121 is generated in the feedback resistor 23, this voltage is negatively fed back, and the deflection current 31 based on the control signal 211 is always supplied to the deflection yoke. It is configured to flow to 30. However, the supply voltage of the amplifier 22 is ± V2. (| ± V1 | <| ± V2 |) The operation principle of the deflection yoke drive circuit configured as described above will be briefly described with reference to FIG. A deflection signal 101 is digitally output from the symbol generator 1 in order to display a predetermined symbol on a CRT by vector scanning. The D / A converter 21 faithfully converts the deflection signal 101 into an analog signal (control signal 2).
11). However, a D / A converter that converts the same deflection signal 101 to analog
From 11, a signal 111 having the same waveform as the illustrated offset current 121 is output. That is, the input bits of the D / A converter 11 are selected so as to perform a binary operation roughly on the basis of the deflection signal 101, and the signal 111 becomes L at time t1 when the deflection signal 101 becomes lower than the predetermined level. Switching to level. Then, the amplifier 12 receiving this signal 111 performs voltage-current conversion and outputs an offset current 121 shown in the figure. The deflection current 31 obtained by superimposing the offset current 121 and the control current 221 output from the amplifier 22 forms a deflection yoke 30
Although the current flows through the feedback resistor 23, the deflection current 31 actually flowing is substantially negatively fed back to the amplifier 22, so that the deflection current 31 is controlled according to the control signal 211, that is, the deflection signal 101. . That is, the addition of the offset current 121 is not affected at all in terms of controlling the deflection current 31. However, in the deflection yoke drive circuit, the power consumption of the amplifier 22 can be kept low without impairing the high-speed controllability of the deflection current 31 for the following reason. That is, the deflection current 31 is changed to the offset current 121 and the control current 221.
The reason is that the DC change in the deflection signal 101 is processed by the offset current output circuit 10, while the AC change is processed by the deflection current control circuit 20. Means As a result, the absolute amount of the control current 221 flowing out or flowing from the amplifier 22 can be reduced by the offset current 121, and at the same time, the power consumption of the amplifier 22 can be suppressed. In the present embodiment, the deflection yoke drive circuit of the display device mounted on an aircraft has been described. However, when the deflection yoke drive circuit is mounted on an aircraft, it is particularly significant that power consumption can be reduced. And the deflection current control circuit 20 are connected in parallel, so that they are fail-safe (double protection).
There is also an advantage that it can have the role of. The deflection yoke drive circuit is not limited to the above-described embodiment. For example, a DC component of the control signal may be extracted by a low-pass filter for an offset current output circuit. In addition, the present invention is not limited to the use of only the vector scanning type display device, but can be applied to a vector / raster mixed type display device. As described above, in the case of the deflection yoke drive circuit according to the present invention,
Since the offset current generated by the offset current output circuit flows in the deflection yoke in addition to the current generated by the deflection current control circuit, even when the deflection yoke is controlled at high speed, the deflection There is no need to set a large power supply voltage to be supplied to the current control circuit, and low power consumption can be achieved. Moreover, since the withstand voltage of the deflection current control circuit can be set low, the cost of the circuit itself can be reduced. In addition, since the offset current flows through the deflection yoke, the deflection of the CRT can be changed at a high speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit configuration diagram of an embodiment of a deflection yoke drive circuit according to the present invention, FIG. 2 is a timing chart of main signals for explaining the operation, and FIG. FIG. 2 is a simplified circuit configuration diagram of the deflection yoke drive circuit of FIG. 10 Offset current output circuit 101 Deflection signal 121 Offset current 20 Deflection current control circuit 30 Deflection yoke 31 Deflection current

Claims (1)

(57) [Claims] While detecting the magnitude of the current flowing through the deflection yoke,
A deflection current control circuit for generating a current corresponding to a deviation between a current command value given by the input deflection signal and the detection result and outputting the current to the deflection yoke; and an offset current corresponding to an offset value indicating the level of the deflection signal. And an offset current output circuit for generating an output signal to the deflection yoke.