JPS6240952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter type power supply device.

Inverter type power supplies are widely used, for example, as power supplies for X-ray tube devices. Such a power supply device is shown in FIG. 1 and will be explained. This device consists of a DC power supply E, a switch SW for turning on the power supply E, an inverter transformer IT to which the voltage from the power supply E is applied to the intermediate tap, and both ends of the primary winding of the inverter transformer IT. It is composed of two thyristors SCR ₁ and SCR ₂ connected to each other and having different firing phase angles,
The two thyristors SCR ₁ and SCR ₂ are operated in a complementary manner by an SCR control circuit (not shown) to generate a high voltage output on the secondary side of the inverter transformer IT,
The high-voltage output is applied to the X-ray tube XT via a full-wave rectifier circuit DB consisting of a diode bridge. Note that L is a current limiting reactor.

However, in the conventional device described above, the DC power supply E is usually installed at a location far from the inverter transformer HT, and therefore the wiring length between the two becomes long, which increases the inductance component. As a result, there was a problem in that the current rise characteristics at power-on deteriorated. Therefore, there is a problem in that the control circuit including the thyristor malfunctions due to deterioration of the current rise characteristics when the power is turned on. This has caused a problem in that the inverter transformer malfunctions and has an adverse effect on the X-ray apparatus.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an inverter-type power supply device that can guarantee the rise of current when the power is turned on and ensure stable operation. .

The present invention will be specifically explained below using Examples.

FIG. 2 is a circuit diagram showing an embodiment of the device of the present invention. This device consists of a DC power supply E, a power supply switch _SW1 , an inverter transformer IT to which power is supplied to the intermediate tap of the primary winding via the switch _SW1 , and a primary winding of the inverter transformer IT. Two thyristors SCR ₁ connected to both ends of the side windings,
SCR ₂ , an inverter control circuit 1 that controls the operation of the inverter transformer IT, and an inverter control circuit 1 disposed near the primary winding of the inverter transformer IT, and
It is constituted by an impedance compensation circuit 2 connected between the intermediate tap and the ground terminal.
Note that L is a current limiting reactor, and _C3 is a commutation capacitor for applying a reverse bias to one of the thyristors SCR ₁ and SCR ₂ when switching them alternately. The power supply switch SW ₁ has contact a
(INVERTER ON), contact b (BATT・
It has a three-stage switching contact: CHARGE) and contact c (OFF). The inverter control circuit 1 has three contacts a to c common to the power supply switch _SW1 , and a switch _SW2 which is switched in conjunction with the switch _SW1 and whose movable contact is grounded;
A time constant circuit 1a in which a parallel circuit of a resistor R ₂ and a diode D ₁ and a capacitor C ₁ are connected in series between the power supply terminal Vcc and the ground terminal, and the two thyristors.
It has a trigger signal control circuit (for example, an oscillation circuit) 1b for giving a trigger signal to the gates of SCR ₁ and SCR ₂ , respectively, and contacts b of the switch SW ₂ ,
c is connected to the connection point of the time constant circuit 1a via the resistor _R1 , and the connection point of the time constant circuit 1a is connected to the control terminal of the trigger signal control circuit _1b via the inverting circuit IN1. has been done. The impedance compensation circuit 2 includes a parallel circuit of a resistor R ₃ and a diode D ₂ and a capacitor C ₂ connected in series, and is charged with electric charge supplied from a DC power source E. When the trigger signal control circuit 1b is in operation, that is, when the inverter is started, the resistor _R3 is bypassed by the diode _D2 , and power is supplied to the inverter transformer IT in cooperation with the DC power supply E. Note that, for example, an X-ray tube or the like is connected to the secondary output terminals P ₁ and P ₂ of the inverter transformer IT.

Next, the operation of the device will be explained with reference to the timing chart shown in FIG. When the switch SW ₂ in the inverter control circuit 1 is switched to contact b or c, the output point of the time constant circuit 1a is close to the ground potential, so the output of the inverting circuit IN ₁
V ₂ is at "H" level, and therefore,
Trigger signal V ₃ from the trigger signal control circuit 1b,
Both V ₃ ′ are not output. Next, power switch SW ₁ and inverter control circuit 1
Switch SW ₂ inside is contact a (INVERTER ON)
1 of the inverter transformer IT
The capacitor _C2 of the impedance compensation circuit 2, which is near the next winding and connected to its intermediate tap, is charged, and the voltage _V1 between the terminals of the capacitor _C2 approaches the voltage of the DC power supply E. gradually increases. At the same time, charging of the capacitor _C1 in the time constant circuit 1a in the inverter control circuit 1 is started, and the voltage between its terminals is gradually increased. When the voltage between the terminals reaches a predetermined potential, the inverting circuit IN The output of ₁ becomes "L" level. here,
The time t ₁ from the start of charging the capacitor C ₂ of the impedance compensation circuit 2 until the charging voltage reaches the voltage of the DC power supply E (determined by the time constant settings of the resistor R ₃ and the capacitor C ₂ ), _{The time t 2 (} resistance _{R 2} (determined by the time constant settings of the capacitor C ₁ ) so that t ₁ ≪ t ₂ , the charging voltage V ₁ of the impedance compensation circuit 2 will surely match the voltage of the DC power supply E. Thyristors SCR ₁ and SCR ² do not operate until the time becomes almost equal to , and then, after a while, the output V ₂ of the inverting circuit IN ₁ is inverted to "L" level, and at this point, the trigger is started. Trigger signals V ₃ and V ₃ ' having different timings are outputted from the signal control circuit 1b, and based on these, the thyristors SCR ₁ and SCR ₂ are activated.
are switched in a complementary manner, the inverter transformer IT performs an inverter operation, and the X-ray tube and the like are driven by the high voltage on the secondary side of the inverter transformer IT.

In such equipment, inverter transformer IT
An impedance compensation circuit 2 having the same function as the DC power supply E is provided near the primary winding of the DC power supply E, and the inverter is controlled until the voltage of the impedance compensation circuit 2 reaches a voltage almost equivalent to the voltage of the DC power supply E. Since the circuit 1 is not operated and the thyristors SCR ₁ and SCR ₂ are driven only when the voltage of the impedance compensation circuit 2 reaches a sufficient value, the rise of the current when the power is turned on is guaranteed. be able to. Furthermore, as mentioned above, by connecting the impedance compensation circuit 2 to the intermediate tap near the primary winding of the inverter transformer IT,
It is possible to solve the problem of the adverse effect of inductance that exists between the conventional DC power supply E and the inverter transformer IT, and also to reduce the large current flowing at the time of inverter startup between the DC power supply E and the impedance compensation circuit 2.
Since the power is divided into two and supplied from both sides, the surge current of the DC power supply E can be suppressed.
This has the effect of not only preventing the electric charge of the DC power source E from being consumed, but also preventing the control circuit including the thyristor from malfunctioning. Therefore, the operation of the inverter can be stabilized, and a power supply circuit optimal for driving the X-ray tube can be provided.

In the above embodiment, the inverter transformer IT
Although a thyristor is used as a switching element in the above, a transistor may be used instead. Further, instead of the time constant circuit 1a provided in the inverter control circuit 1, a timer, a monostable multivibrator, or the like may be used that generates an inverted output after a predetermined time _t2 has elapsed from startup.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional inverter type power supply device, FIG. 2 is a circuit diagram of an embodiment of the device of the present invention, and FIG. 3 is a timing chart for explaining its operation. 1...Inverter control circuit, 2...Impedance compensation circuit, 1a...Time constant circuit, 1b...Trigger signal control circuit, SW ₁ , SW ₂ ...Switch, IT
...Inverter transformer, SCR ₁ , SCR ₂ ...Thyristor, E...DC power supply, IN ₁ ...Inverting circuit,
C ₁ , C ₂ ... Capacitor, R ₁ to _{R 3} ... Resistor, D ₁ ,
_D2 ...Diode.

Claims (1)

[Claims] 1. An inverter transformer in which a DC input power source, the DC input power source is supplied to an intermediate tap of a primary winding, and two switching elements are connected in series between both terminals of the primary winding; In an inverter type power supply device having an inverter control circuit that starts an inverter by operating the two switching elements in a complementary manner, an intermediate tap of the primary winding near the inverter transformer is provided. A charging/discharging means is provided in the inverter, and is charged by supplying DC input power and discharged when the inverter is started, and acts as a power source. bypass means for bypassing the resistor and discharging to the intermediate tap when the charging/discharging means is discharging; An inverter type power supply device characterized by comprising a time limit means for operating a control circuit.