JPS583382A - Power supply for dc-dc converter - Google Patents

Abstract

PURPOSE:To increase the efficiency of pre-heating, by suitably selecting the rate of reduction of an output voltage of the secondary winding and a heater winding of a converter transformer at preheating to the output voltage in normal operation. CONSTITUTION:At normal operation, a switch 22' is connected to a heater voltage output terminal 23A and a current is applied from the terminal 23A to a heater H. At pre-heating, the switch 22' is changed over to a voltage output terminal 11. The terminal 11 outputs a higher output voltage than a heater voltage and a power is applied to a circuit load 25 of the device. At pre-heating, a DC voltage is applied to a control terminal 19' with a switch 20' interlocked with the switch 22' to lower an output voltage of each output winding of a converter transformer T. The rate of reduction of an output voltage at the transformer T at pre-heating to that of the secondary winding 6 and a heater winding 12 is almost made equal to the winding ratio of the intermediate tap of the primary winding 5 to the winding 12, allowing to apply a voltage of the same degree of the heater H both at normal and pre-heating states.

Description

Detailed Description of the Invention This invention supplies power to the heater and cathode ray tube drive circuit of a cathode ray tube used in television cameras, etc., and also supplies power to the heater of the cathode ray tube in advance to preheat the heater before the cathode ray tube is manufactured. DC-D with ant heat function
This relates to a C converter power supply.

In order to preheat the heater of the cathode ray tube before operation of the cathode ray tube, components and electric power for preheating are required, such as the use of a heater transformer in the case of an AC power supply drive.

On the other hand, in the case of small devices that drive cathode ray tubes using battery power, such as TV cameras, when the cathode ray tube is in full operation, the previous converter is stopped to avoid wasting power, and the DC power source is Voltage is supplied from the battery output to the heater via a series impedance such as a resistor.A conventional switching regulator type DC-DC converter power supply having such a configuration is shown in Figure 1.Figure 91 , the primary winding 5 of the converter transformer T is connected to the DC power input terminal l and the collector of the field switching transistor 4, and the base of the switching transistor 40 is connected to the error amplifier lI2 and the pulse It is switched and driven by the control circuits 3 and K.The secondary winding 6 of the converter transformer T is equipped with rectifier diodes 7, 1 and 1 to extract various voltages necessary for driving the cathode ray tube 24 and for the equipment circuits. 9 and a smoothing capacitor 8.IQi are connected. Since the heater current is generally large, a converter transformer TK heater winding @12 is provided, and the heater voltage is applied to the heater voltage output terminal 23A by the rectifier diode 13 and the smoothing capacitor 14. In the case of multiple outputs, the voltage at the voltage output terminal, for example 11, which generally requires stabilization accuracy, is divided by the detection resistor 15, 16 and applied to the input terminal 17 of the error amplifier 112, and the voltage at the reference voltage terminal 18 The pulse control circuit 3 is compared with a reference voltage vR applied to the voltage terminal 11, and is controlled so that the output voltage at the voltage terminal 11 is a constant voltage.The pulse control circuit 3 is essentially the same in the case of a self-excited converter or a separately excited converter. In the case of Fig. 1, the DC voltage 10B- seen at the DC power supply switch IKm is flll
Since the switching regulator system is used to obtain a stabilized output even when the output voltage is J, an error amplifier 2 is present. So-called DC-D without amplifier 2
Becomes the C converter power supply.

In the C-DCC comparator power supply as described above, the heater H of the cathode ray tube 24 is normally connected to the heater voltage output terminal 2.
Switch 22 is connected to 3A, and heater winding Jl1
Heater voltage is applied from switch 2, switch 20 connected to switch 22 is connected to ground terminal 26AK, and normal switching operation is performed.

On the other hand, during preheating, the switches 20 and 22 are connected to the terminals 26B and 23B, respectively, and the switching operation is stopped by applying a control voltage to the stop control terminal 19 of the switching regulator.
-Reduce. Heater H has DC power input terminals 1 to 1.
Current is supplied through the reheating resistor 21.

Such a conventional DC-DC converter power supply can avoid wasting power during one reheating of the cathode ray tube drive circuit, has a simple configuration, and has the advantage of being easily compatible with various heaters. However, in general, when the rated voltage of the heater is lower, the power consumption by the resistor 21 increases and the efficiency decreases, especially when the heater voltage is 2.8V.
If the input power is low, such as a DC voltage of 12V, which is commonly used as a DC voltage of 10B, this becomes a problem.

Therefore, an object of the present invention is to provide a DC-DC converter power supply that has high efficiency during preheating and has a small number of parts.

An embodiment of the present invention is shown in FIGS. 2 and 3. In other words, this DC-DC converter power supply can be used for one operation of the error amplifier 2 by switching the switch 20"j- as shown in FIG. The state at is changed, thereby changing the operating state 11t of the pulse control circuit 3, and the output voltage of the secondary winding 6 and the heater winding 12 of the converter transformer T during preheating is reduced from the normal output voltage. , and by switching the switch 22' which is interlocked with the switch 20', the rectifier diode 13 is normally connected to the output winding 12.
The heater HK power is supplied through the smoothing capacitor 14, and the heater HK power is supplied from the intermediate tap of the secondary winding 6 through the diode 9 and the capacitor 10, that is, from the terminal 11, so that the heater HK power is supplied through the terminal 11 during preheating. Secondary winding 6 and heater winding l of converter transformer T
By making the reduction ratio of the output voltage of l112 with respect to the normal output voltage approximately equal to the turns ratio of the intermediate tap of the primary winding 5 of the converter transformer T to the heater winding 12, the heater H.K.
I try to apply the same voltage.

To explain in more detail, during normal operation, current is supplied to the heater H from the heater voltage output terminal 23A. next,
During preheating, the output switch 922' is switched to the voltage output terminal 11. In the previous work under normal conditions, the voltage output terminal 11 is a necessary terminal that outputs an output voltage level higher than the heater voltage and supplies power to the circuit load 25 of the device. Switch 20' interlocking with heater selection switch 22'
At the same time, in order to suppress the converter output by several times the normal IK, a DC voltage of 10 B is applied as a control voltage to the control terminal 19', and the pulse width, duty ratio, oscillation wave number, etc. Reduces the output voltage available through the output winding. The control terminal 19' is connected to the error amplifier 2.
The case where the operation of the error amplifier 2 is changed is shown as an example.
In the case of a simple DC-DC converter without a DC-DC converter, it goes without saying that it is possible to change the previous version of the pulse control circuit 3. If the heater is capable of applying alternating current, the same result can be achieved even if the winding taps are switched. Switching production is possible.

Figure Wi3 shows a circuit that embodies the circuit of Figure 2. To explain the operation during preheating, when the switch 43 is connected to DC voltage +BK, the switching control terminal 42 is positively biased, the transistor blades are turned on by the resistors 35 and 34, and the reference input voltage of the error amplifier 2 is: It is lowered by the ratio of resistor 31 and resistor 32 compared to the normal reference voltage ■R.

As a result, the RIC-DC converter power supply operates to reduce the output. A variable resistor 44 located between the feedback resistors 15 and 16 is used for voltage setting during normal operation. Switching control terminal 4
The voltage applied to 2 turns on transistor 39 through resistor 36,37.

In order to turn on the transistor 39t later than the transistor 33, a capacitor 38 is added. The collector of the transistor 39 is connected to the pace of a transistor 41 for switching the heater, the collector of the transistor 41 is connected to the -H terminal, and the output terminal of the transistor 41 is connected to the voltage output terminal 11. The resistor 40 is inserted for stabilization so that the transistor 41 is completely off during normal operation. After the first converter operation goes down as described above, the heater voltage is applied to the heater H from the voltage output terminal 11 which generates a voltage higher than the heater voltage output terminal 23A, and the preheat 1993 operation is performed with a small amount of power. I.J.
When it heats up, the output is reduced and there is still some power left from the DC-DC converter to the cathode ray tube drive circuit.
Since the voltage supplied to the heater HK can almost match the heater voltage, there is no need for a voltage drop resistor, and there is no power loss due to it. If the power consumption of the circuits other than the -1 power is originally low, the total power consumption during preheating will be extremely low.

As described above, it is possible to reduce the power consumption t' during preheating by eliminating the heating resistor tube for voltage adjustment with a simple configuration, but let's compare it with a specific practical voltage. For small video cameras, the camera tube heater is suitable for power saving.
- For example, a heater voltage of about 110 mA with a heater voltage of 2.8 V has been used recently. -The most common DC voltage input to the circuit is 12V, and 12V (2)
[Each electrode voltage and circuit voltage are obtained by boosting the current voltage.

As camera equipment becomes smaller, the power of the load circuit including the heater is becoming less than 2W111. And DC-D
The power output from the C converter intersects after lW# and is 9v
Quality is often achieved through serial control starting at 12V. Comparing the total power per hour in such cases, we can see that in the past, if 80 watts of power were added to the heater, it would be 12V.
X(110mAX0.8)=1056mW is consumed from the power supply of DC voltage +B. At this time, the DC-DC converter is stopped, so the power consumption of the converter output is OW.

On the other hand, in the case of the embodiment, for example, if the voltage output terminal 11 is a stabilized output terminal of 15 V during normal operation, the converter output voltage is switched by the control terminal 19 to about 1 during preheating. As a result, assuming that a voltage of approximately 2.8 V is applied to the heater, 300 mW will be consumed. In addition, the load voltage of other high voltage lines is approximately 1
Therefore, 1, so the total is 440 mW (from i, it can be seen from the comparison above that the wasted power consumption during preheating is less than 1. When the DC voltage is 12V The same effect as in 4 can be realized with a higher voltage, for example, 24V, and the output can be lowered by an appropriate duty ratio.

The above effects become more effective as equipment becomes smaller and its power consumption ratio increases.
The lower the heater voltage, the higher the voltage.

As described above, the DC-DC converter power supply of the present invention includes a converter transformer having a primary winding, a secondary winding, a heater winding with a smaller number of turns than the secondary winding, and a Next volume 11kKK rows of 11 switching elements, a pulse control circuit that turns these switching elements on and off, and a rectifying and smoothing circuit that rectifies the output of the secondary winding of the 1IiTE humbverter transformer and supplies it to the cathode line circuit. and 2 of the converter transformer during preheating.
a first switch that changes the operation of the pulse control circuit so as to reduce the output voltage of the next winding and the heater winding from the normal output voltage; 1ItI so as to supply power to the cathode ray tube's terminal and also to supply power to the cathode ray tube's terminal from the secondary winding of the front six converter transformers during preheating.
a second switch that is switched in conjunction with the first switch; and a reduction ratio t#1tI of the output voltage of the secondary winding and the heater winding of the converter transformer with respect to the normal output voltage during preheating. Since the turn ratio is made approximately equal to the turn ratio of the heater winding of the converter transformer to the secondary winding, the efficiency during preheating is high and the number of parts can be reduced to simplify the circuit configuration.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional DC-DC converter power supply, v
II! Figure 12 shows -Ij! of this invention. Example circuit diagram, 3rd
The figure is a specific circuit diagram. T...Converter transformer, 2...Error increase 118.
3... Bar A'X control circuit K, 4... Switching transistor, 5... Primary winding, 6... Secondary winding, 7.
9...Diode, 8.10...Capacitor, 20
'...Switch, 22'...Heater selection switch,
24...Shade 1if%H...Heater

Claims (1)

[Claims] The primary winding, the secondary winding, and the number of turns smaller than the secondary winding.
a converter transformer having a P winding; a switch element connected in series to the primary winding of the converter transformer; a pulse control circuit for turning on and off the switch element; and a pulse control circuit for rectifying and smoothing the output of the secondary winding of the converter transformer. and a rectifying and smoothing circuit that supplies the output voltage to the cathode wire section front circuit, and the pulse voltage so as to reduce the output voltage EE of the secondary winding and heater winding of the converter transformer at one time from the normal a power voltage. The first (D switch 4f) that changes the operation of the control circuit, and 71 normally supply power to the heater winding of the RK pre-heat converter transformer and the heater of the cathode ray tube, and also the secondary winding of the K11ll converter transformer during preheating. a second switch that is switched in conjunction with the first switch so as to supply power to the heater of the cathode ray tube; A DC-DC converter power supply whose reduction ratio tU relative to the normal output voltage is approximately equal to the turns ratio of the heater winding of the converter transformer to the secondary winding.