JPH0733587Y2 - DC power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention mainly relates to a high-voltage DC power supply device used as a power source for an X-ray generation source.

[Prior Art] An example of a conventional DC power supply device is shown in FIG. In the figure, a DC power supply device includes a DC power supply 12 composed of a commercial power supply 10 and a power supply rectifier 11, and an inverter circuit 13 for converting a DC input into an AC output by opening / closing switching elements Q1 to Q4.
And an output rectifier circuit 14 that converts the AC output to DC output.
A setting circuit 15 that outputs a setting signal a corresponding to a desired DC output voltage level, an output voltage detection circuit 16 that detects a DC output voltage, an X-ray tube 17 that is a load, and a tube current adjustment circuit thereof. 18 and a control circuit 19 for controlling the opening and closing of the switching elements Q1 to Q4. The control circuit 19 receives the setting signal a and obtains the desired DC output. ~ Control the opening and closing of Q4. Here, the control circuit 19 also receives the feedback voltage signal b corresponding to the DC output voltage from the output voltage detection circuit 16, and finely adjusts the opening / closing control according to the actual DC output voltage.

The inverter circuit 13 includes a transformer T1, a choke coil L0, and energy regeneration diodes FD1 to FD4.
When the switching elements Q1 to Q4 are turned off, the energy stored in the choke coil L0 is regenerated to the smoothing capacitor FC of the power rectifier circuit 12 through the regenerative diodes FD1 to FD4. .

[Problems to be Solved by the Invention] In the above configuration, when the X-ray tube 17 is used as an X-ray generation source for X-ray analysis, the output current i0, that is, the tube current of the X-ray tube 17 is close to the rated value. Output voltage Vc
It is required to have a usage method that changes the value to 1/2 or 1/3 of the rating. This output voltage is selectively set in the setting circuit 15 by an operation from the outside, for example.

However, if the output voltage Vc is reduced while keeping the output current i0 constant, the surplus energy accumulated in the choke coil L0 increases, so when regenerating this surplus energy, the regenerative diodes FD1 to FD4 that form the regenerative circuit. The loss due to the resistance of the smoothing capacitor FC, the choke coil L0, and the wiring connecting these elements inevitably increased, resulting in a decrease in conversion efficiency.

The present invention has been made to solve the above-mentioned problems, and in accordance with a change in output voltage, that is, a change in set voltage,
By changing the inductance of the inverter circuit 13, it is intended to suppress the loss during regeneration and prevent a decrease in conversion efficiency.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a variable inductance circuit which constitutes an energy storage inductance element in an inverter circuit, and a setting signal output from a setting circuit. And an inductance adjusting circuit for changing the inductance of the variable inductance circuit.

[Operation] According to the present invention, the excess energy regenerated is held at a substantially constant value by changing the inductance of the inverter circuit according to the change in the output voltage, that is, the change in the level of the setting signal. Even when the voltage changes, the loss during regeneration is suppressed, and the conversion efficiency is prevented from decreasing.

[Embodiment] FIG. 1 is a circuit diagram of a DC power supply device showing an embodiment of the present invention. The same parts as those in FIG.

The power supply rectifier 11 of FIG. 1 includes a rectifier diode 21, the inverter circuit 13 also includes diodes 22 and 23, and the output rectifier circuit 14 includes a bridge-type full-wave rectifier 25 and a smoothing capacitor.
Equipped with 26. Further, the setting circuit 15 has terminals 27 to 29 to which signals corresponding to three different output voltages V1, V2, V3 are input.
And a selection switch 30 for selecting these terminals 27 to 29 by an external manual operation and outputting a setting signal a corresponding to the desired DC output voltage levels V1, V2, V3.
For example, the voltage level V1 above is the rated voltage, and V2 is 1/1 of the rated
2, V3 is 1/3 of the rating. The control circuit 19 includes an oscillator circuit 31,
A pulse width control circuit 32 and a drive circuit 33 are provided.

The above-mentioned configuration is the same as the conventional one, and the feature of the present invention is that the inductance of the variable inductance circuit 41 that configures the inductance element for energy storage in the inverter circuit 13 and the inductance of the variable inductance circuit 41 according to the level of the setting signal a are set. That is, an injectance adjusting circuit 42 for changing is provided. In this embodiment, the variable inductance circuit 41 has three choke coils L1, L2 and L3 having different inductances, and the inductance adjusting circuit 42 has a judging circuit 43 for judging the level of the setting signal a, It has a selection circuit 44 which selects any one of the above three choke coils L1, L2 and L3 in accordance with the result of the judgment and which is connected in series to the transformer T1.

Next, the principle of the present invention will be described before the operation of the above embodiment is explained.

FIG. 2 shows an equivalent circuit obtained by simplifying the switching elements Q1 to Q4 to the rectifying and smoothing output portion in FIG. 1 and extracting only a half cycle. In FIG. 2, a switch S is a pair of switching elements Q1 and Q4 operating in pairs.
Alternatively, in Q2 and Q3 (Fig. 1), L is the choke coil L1 to L3.
, C is the circuit capacitance including the output side capacitor 26, and RL is the load resistance of the X-ray tube 17.

The operation waveforms of FIG. 2 are shown in FIG. In FIG. 3, assuming that the period during which the switch S (FIG. 2) is ON within the half cycle period T is t1, the current iL flowing through the inductance L in this period t1 linearly increases to the peak value ip. . The charge QL passing through the inductance L during the ON period t1 and the charge Q0 passing through the load RL during the half cycle period T are respectively Q0 = i0 · T (1) And when these charges QL and Q0 are equal, from equation (1) = equation (2), Therefore, Becomes If the output voltage VC is constant (ignoring ripples), the voltage VL applied to the inductance L is generally Therefore, Becomes Substituting equation (3) into this, Therefore, the output voltage VC is As is clear from this equation (4), the switch ON period t1
When the output current i0 is constant, the output voltage VC is
When is constant, the output current i0 is increased or decreased.

The energy EL stored in the inductance L by one switching in the half cycle period T is shown by EL = VL.t1 (5), which is the energy of the switching elements Q1 to Q4 in FIG.
When OFF, as described later, regenerative diodes FD1 to FD4
Is regenerated through the smoothing capacitor FC. That is, the energy of the inductance L reciprocates between the smoothing capacitor FC on the power supply side and the inductance L at each switching.

Here, when the output voltage VC is reduced while the output current i0 is kept constant by shortening the switch ON period t1, the inductance VL is constant and the voltage VL increases as can be seen from FIG. . At this time, the energy EL stored in the inductance L is calculated from the equation (5) as follows: Therefore, this energy EL also increases as the switch ON period t1 is shortened, that is, the output voltage VC is reduced.

Since the energy EL is regenerated by the smoothing capacitor FC as described above, this regenerated energy also increases. As a result, the regenerative diodes FD1 to FD4, choke coils L1 to L3, and smoothing capacitors shown in FIG.
The loss due to the resistance of FC and the wiring connecting these elements inevitably increases, resulting in a decrease in conversion efficiency.

In order to avoid this situation, in the present invention, in the equation (6), the inductance L is changed in proportion to the ON period t1, and as a result, the energy EL is set to a substantially constant value corresponding to the optimum value. That is, the present invention operates as follows.

In FIG. 1, first, the basic power conversion operation is the same as the conventional one, and, for example, by manually operating the operation unit (not shown) of the setting circuit 15 from the outside,
30 is operated to select one of the three voltage levels V1, V2, V3 of the desired DC output voltage VC, and the setting circuit 15 outputs the setting signal a. Pulse width control circuit 32 of control circuit 19
Is a constant reference pulse signal p1 output from the oscillation circuit 31.
And the setting signal a, the reference pulse signal is set so that the pulse width becomes narrower as the level of the setting signal a becomes lower.
The pulse width of p1 is controlled in three steps. At this time, the pulse width control circuit 32 receives the DC output voltage VC from the output voltage detection circuit 16.
Also, the feedback voltage signal b corresponding to is received, and the pulse width is finely adjusted according to the actual DC output voltage VC.

The pulse signal p2 whose pulse width is controlled in this way is input to the drive circuit 33, and drive signals d1 to d4 corresponding to the pulse width are output from this drive circuit 33, and the switching elements Q1 to
Q4 is opened and closed. At this time, the two switching elements Q
1, Q4 are simultaneously opened and closed and turned on for a time t1, and at the opposite timing, the other two switching elements Q2 and Q3 are simultaneously opened and closed and turned on for a time t1. As a result, an alternating current is supplied to the transformer T1, and this alternating current is supplied to the transformer.
Full-wave rectifier of output rectifier circuit 14 after voltage conversion at T1
It is rectified by 25, smoothed by the capacitor 26, and then supplied to the X-ray tube 17.

Here, the variable inductance circuit which is a feature of the present invention
41 and the inductance adjustment circuit 42 perform the following operations. That is, the determination circuit 43 of the inductance adjusting circuit 42 receives the setting signal a, determines the level of the setting signal a, that is, the level of the output voltage VC, drives the selection circuit 44 according to the determination result, and sets Select the choke L1, L2, L3 from the one with the largest inductance according to the case where the level of the signal a is V1 which is the rated voltage V1, 1/2 which is V2 and V3 which is 1/3 of the rated voltage. Connect to T1 in series.

The switch ON time t1 changes to 1: 1/2: 1/3 corresponding to the level of the setting signal a, that is, the level of the output voltage VC. On the other hand, the inductance of the chokes L1, L2, L3 is, as described above using the equation (6), the switch ON time t1.
It also changes to 1: 1/2: 1/3 in proportion to and keeps the energy EL accumulated in the chokes L1, L2 or L3 constant. This accumulated energy EL is FD1 → L1 (L2, L3 done) → FC
→ FD4 or FD3 → L1 (L2, L3) → FC → FD2 is regenerated to the smoothing capacitor FC. Since the amount of regenerated energy is equal to the accumulated energy EL,
Even if the level of the setting signal a (the level of the output signal VC) decreases, it does not increase and is kept constant. Therefore,
Even when the output voltage VC is reduced, the loss in the regenerative circuit is suppressed.

As a method of changing the inductance of the choke, in addition to the above-described embodiment, a method of changing the coil winding pitch, a method of using a Brooks mutual inductor, a method of using a supersaturated reactor, etc. can be applied.

The method of varying the winding pitch of the coil is to wind a single-layer solenoid coil with a relatively rigid single wire, fix one end thereof, and mechanically move the other end along the axis of the coil,
Inductance is varied, and the method of using the Brooks mutual inductor is to vary the relative position of two sets of coils connected in series to vary the coupling coefficient and vary the inductance as a whole. .
Further, the method of using a supersaturated reactor is a supersaturated reactor having two sets of coils, one set of coils is used as a choke coil, a DC bias current is passed through the other coils, and this current is changed, The effective permeability of the magnetic core is changed to change the inductance.

[Effects of the Invention] As described above, according to the present invention, the excess energy regenerated is changed to a substantially constant value by changing the inductance of the inverter circuit according to the change of the output voltage, that is, the level change of the setting signal. Therefore, even when the output voltage changes, the loss during regeneration is suppressed, and the decrease in conversion efficiency is prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an equivalent circuit of FIG. 1, FIG. 3 is a signal waveform diagram of the equivalent circuit, and FIG. 4 is a circuit diagram of the equivalent circuit. FIG. 5 is a characteristic diagram showing voltage distribution, and FIG. 5 is a circuit diagram showing a conventional example. 12 ... DC supply source, 13 ... Inverter circuit, 14 ... Output rectifier circuit, 15 ... Setting circuit, 19 ... Control circuit, 41 ... Variable inductance circuit, 42 ... Inductance adjustment circuit, a ... Setting Signal, FC, FD1 to FD4, L1 to L3 ... Regenerative circuit, VC ... Output voltage.

Claims (1)

[Scope of utility model registration request] 1. An inverter circuit for converting a DC input from a DC supply source into an AC output by opening and closing a switching element, an output rectifier circuit for converting the AC output into a DC output, and a voltage level of a desired DC output. A setting circuit for outputting the setting signal, a control circuit for receiving the setting signal and controlling the opening and closing of the switching element so as to obtain the desired DC output, and the surplus energy accumulated in the inverter circuit. In a direct-current power supply device including a regenerative circuit for regenerating a direct-current supply source, a variable inductance circuit forming an inductance element for energy storage in the inverter circuit, and an inductance of the variable inductance circuit according to the level of the setting signal are set. By changing it, it is possible to keep the above-mentioned regenerated surplus energy almost constant. A direct current power supply device comprising: a conductance adjustment circuit.