JPS63257463A - Switching power source device - Google Patents

Abstract

PURPOSE:To effect ON/OFF control stably, by a method wherein a predetermined timing before the intersection between an oscillating voltage, induced in the primary coil of a transformer, and zero level is caught to put a switching element ON while estimating the intersection to occur thereafter. CONSTITUTION:In a switching power source device, the primary coil 6a of a booster transformer 6 and a switching circuit 4 are connected to both terminals of a DC power source 1 in series while a resonance capacitor 5 is connected in parallel to the switching circuit 4. A transformer voltage detecting circuit 2 is connected to both terminals of the primary coil 6a of the booster transformer 6 and an ON/OFF control circuit 3 is connected to the output side of the voltage detecting circuit 2, further, the switching circuit 4 is connected to the output side of the control circuit 3. The booster transformer 6 is equipped with respective windings for a magnetron 8 at the output side thereof. According to this method, the switching circuit 4 may be turned OFF with a timing, at which an impressing voltage becomes zero, whereby a switching loss may be eliminated and the title device may be operated stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching power supply device, and in particular to switching on a switching element in a voltage resonant switching power supply device that supplies power to a load with unstable power consumption.・
Regarding off control.

[Conventional technology]

The power supply device that supplies power to the magnetron is disclosed in U.S. Patent No. 339.
As described in the specification and drawings of No. 6342, a leakage transformer is used as a step-up transformer to keep the anode current of the magnetron constant against fluctuations in the commercial power supply voltage, and a transformer is used to prevent a drop in the power factor. A capacitor is connected in series to the secondary winding. However, since such a power supply device drives the step-up transformer at the low frequency of the commercial power supply, it has been difficult to reduce the size and weight of the power supply device.

For this reason, a high frequency switching power supply device that drives a step-up transformer with high frequency has been proposed. The 10th example of this is a voltage resonant switching power supply.
This will be explained using the drawings and FIG. 11.

The switching 'r4 power supply device shown in FIG.
, a control circuit 32, a switching transistor 33 controlled on/off by the control circuit 32, a damper diode 34 and a resonance capacitor 35 connected in parallel with the switching transistor 33, the switching transistor 33, the damper diode 34, and a resonance capacitor 35. The DC power supply 31 is connected to the DC power supply 31 through a parallel circuit of a capacitor 35.
A step-up transformer 36 is provided, the primary winding 36a of which is connected to the step-up transformer 36.

In the switching source device configured as described above, the switching transistor 33 is turned on and off by the control circuit 32.
The switching transistor 33 is turned on and off.
Power is supplied to the load circuit from the secondary winding 36b of the step-up transformer 36, whose current in the primary winding 36a is interrupted when the transformer is turned off.

FIG. 11 shows the voltage and current waveforms of the switching transistor 33 and damper diode 34 when the operation of this switching power supply device is in a steady state. Here, the switching transistor 33 operates from t0 to tI+t!
~t, and t4~t,.

period is on state, tI ``”l + t3'~t
, is in the off state. When the switching transistor 33 is in the on state, the excitation current and the load current of the transformer 36 are applied to the switching transistor 33 in the 11th
It flows as shown in figure (2). And tIn jil+
When the switching transistor 33 turns off at timing t, the current flowing in the transformer 36 flows into the resonance capacitor 35, and an oscillating voltage is generated due to the series resonance effect of the inductance of the primary winding 36a of the transformer 36 and the resonance capacitor 35. is switching transistor 3
given to 3. This oscillating voltage is t! Then, at the timing t4, the damper diode 34 is turned on and current flows in the negative direction. This operation reduces duplication of voltage and current during switching, resulting in a power supply device with low loss.

In order to effectively utilize resonance characteristics in such a voltage resonance type switching power supply device, the timing for issuing an on signal that turns on the switching transistor 33 must be accurate. For this reason, there is a method that detects when the voltage of the switching transistor becomes 0 and generates the next on signal, and a method that detects the current of the damper diode and generates the next on signal as described in Japanese Patent Application Laid-Open No. 55-122479. A method of generating is described.

However, such an ON signal generation method causes the following problems in a switching power supply device that supplies power to a load such as a magnetron that has an unstable load state. This problem will be explained using FIGS. 12 to 14.

FIG. 12 shows an example in which the magnetron 38 is driven by the switching power supply device described above. The next winding 36c is connected to drive the filament.

Figure 13 shows the magnetron 38 that is powered in this way.
It shows the anode voltage characteristics and anode current characteristics of , where (1) is the anode voltage characteristic and (2) is the anode current characteristic. The actual anode voltage and anode current are pulsating or intermittent, but in a high-frequency switching power supply, the pulsating and intermittent periods are extremely short, so they are averaged and shown.

When the power is turned on at timing t, the electron beam cannot be emitted from the cathode to the anode because the filament of the magnetron 38 is insufficiently heated at this time, and the anode current is in a state of 0. In such a state, the high voltage output system of the switching power supply is in a no-load state, so the anode voltage of the magnetron 38 is higher than in the steady state.

This state continues until the heating of the filament of the magnetron 38 progresses and an electron beam is generated (this state is called a starting state). When the heating of the filament progresses and the timing of tX arrives, the electron beam stops. This occurs in a stable state, and as a result, the anode current begins to flow, and the anode voltage decreases accordingly (this state is called a critical state). When the heating of the filament is completed at timing 1, the generation of the electron beam becomes stable (this state is referred to as a steady state).

Normally, the time from turning on the power until reaching a steady state is about 3 seconds.

Next, the operating states of the switching power supply device in the starting state, critical state, and steady state will be explained using FIG. 14.

In FIG. 14, (1) shows the voltage of the switching transistor 33, and (2) shows the current.

The starting state and the steady state have different magnitudes of voltage and current, but exhibit the voltage and current characteristics as described above. However, in the critical state, the anode current of the magnetron 38 flows irregularly, causing the circuit to deteriorate. The resonance effect is disturbed,
As at timing t, an abnormal phenomenon occurs in which, even when the voltage of the switching transistor 33 should normally cross the 0 level, it does not become 0 and then rises again.

Conventionally, when the timing to start turning on the switching transistor 33 is controlled by detecting the zero point of the current of the damper diode 34 or the voltage of the switching transistor 33, if an abnormal phenomenon as described above occurs in a critical state, the switching The on-start timing of the transistor 33 is disturbed and normal switching operation cannot be performed.

[Problem that the invention seeks to solve]

As described above, the conventional voltage resonance type switching power supply device has a problem in that if the load thereof consumes power irregularly, normal switching operation cannot be performed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a switching power supply device that can maintain a stable operating state even if the load involves irregular power consumption.

[Means for solving problems]

In order to achieve this object, the present invention provides a control circuit that controls on/off of a switching element connected to a primary winding of a transformer. transformer voltage detection means for detecting voltage, and one of the transformers during the off period of the switching element based on the detected voltage output from the transformer voltage detection means.
Discrimination means for determining when the oscillating voltage reaches a predetermined set value in a region where the oscillating voltage, which is induced in the next winding and has a polarity opposite to the conduction polarity of the switching element, changes toward the conduction polarity of the switching element. The present invention is characterized in that a discrimination signal delaying means is provided for delaying the discrimination signal outputted from the discrimination means to generate an ON start signal for the switching element.

And the second invention is a control circuit that controls on/off of a switching element connected to the primary winding of a transformer.
transformer voltage detection means for detecting the voltage induced in the primary winding of the transformer; detection voltage delay means for delaying the detected voltage output from the transformer voltage detection means; A delayed detection voltage output from the detection voltage delay means in a region where an oscillating voltage of opposite polarity to the conduction polarity of the switching element induced in the primary winding changes toward the conduction polarity of the switching element, The present invention is characterized in that an on-signal generating means is provided for detecting that the voltage reaches a predetermined voltage value and generating an on-start signal for the switching element.

[Effect]

The first invention captures a predetermined timing before the oscillating voltage induced in the primary winding of the transformer crosses the O level, and predicts that the oscillating voltage will cross the 0 level after a predetermined time from this timing. to turn on the switching element. Therefore, even if an abnormal phenomenon occurs in which the oscillating voltage is disturbed near the 0 level and does not cross the 0 level, a control signal that turns on the switching element is reliably generated.

The second invention detects the delayed vibration voltage induced in the primary winding of the transformer by predicting the timing at which the actual vibration voltage intersects the O level. It is sufficient to detect that the voltage reaches a predetermined value before crossing the 0 level, and therefore, even if the actual oscillating voltage is disturbed near the 0 level, it will not be affected by the disturbance.

〔Example〕

Example 1 An example of the present invention will be described below with reference to FIGS. 1 and 2.

The switching power supply device shown in FIG.
are connected in series, and a resonant capacitor 5 is connected in parallel with this switching circuit 4. A transformer voltage detection circuit 2 is connected to both ends of the primary winding 6a of the step-up transformer 6.
An on/off control circuit 3 is connected to the output side of the transformer voltage detection circuit 2, and a switching circuit 4 is connected to the output side of the on/off control circuit 3.

On the other hand, on the output side of the step-up transformer 6, there are an anode voltage application winding 6b and a filament power supply winding 6C of the magnetron 8, and a high voltage rectifier circuit 7 is connected to the anode voltage application winding 6b. Here, the power supply for the filament may be supplied by adding a rectifier circuit or from a separate power supply.
Further, although the high voltage rectifier circuit 7 uses a half-wave voltage doubler rectification method as an example, other rectification methods may be used.

Next, the operation of the circuit configured as described above will be explained with reference to FIG. Figure 2 (1) shows the current flowing through the switching circuit 4, and Figure 2 (2) compares the voltage applied to the switching circuit 4 with this voltage of the switching circuit 4 in order to detect a predetermined change in the transformer voltage. The input voltage Ein to be
(3) in the same figure shows the output signal of the comparison result, (4) in the same figure shows the signal obtained by delaying the output signal in (3) by the time τ, and (5) in the same figure shows the on/off control of the switching circuit. The drive signals are shown respectively.

Timing t0 to t is a period in which the switching circuit 4 is on, and the current of the switching circuit 4 increases as shown in (1). And 1. When the switching circuit 4 is turned off at the timing of , the current flowing through the switching circuit 4 becomes 0, and the applied voltage has an oscillating waveform as shown in (2).

After further time elapses, at the timing of 1t, the voltage applied to the switching circuit 4 becomes O, so if the switching circuit 4 is turned on at this time, a t'dJX device with almost no switching loss can be obtained.

The transformer voltage configuration circuit 2 and the on/off control circuit 3 function to obtain such timing for turning on the switching circuit 4. These circuits compare the voltage of the DC power supply 1, that is, the input voltage Ein of the switching power supply, and the voltage applied to the switching circuit 4, and form a signal as shown in (3) in FIG. This signal is the step-up transformer 601
Since the oscillating voltage generated in the next winding 6a is generated at a timing before it crosses the 0 level, it cannot be used as a signal for driving the switching circuit 4 as it is. Therefore, the switching circuit 4 shown in (2) of FIG.
Timing when the voltage crosses the 0 level 1. In order to adjust the time to , the signal in (3) is delayed by the time τ. The delayed signal is shown in (4). Then, the next ON signal is generated in synchronization with the time when the signal (4) goes from 1 to O. Note that the off timing is determined by time management from the on start timing.

In such an operation, the waveform when the operation of the magnetron 8 is in a critical state and the resonance condition is disturbed is shown at t4 in FIG. At this time, the voltage of the switching circuit 4 continues to fall until t4, but since the resonance conditions are disturbed, after t4 it rises as indicated by the dotted line and may become a voltage waveform that does not cross the O level. Even in such a state, if the circuit of this embodiment is used, the switching circuit 4 can be turned on reliably at the timing t4, and stable operation can be maintained. In addition, the problem at this time is that since some switching circuit voltage remains, the switching circuit 4 short-circuits the resonant capacitor 5 connected in parallel with the switching circuit 4, and the current flowing through the switching circuit 4 becomes a larger value at t4 than in the steady state. However, even though the switching circuit voltage remains, since it is turned on at around the minimum voltage, the switching circuit current at this time does not increase so much, and the switching element will not be destroyed.

As described above, according to this embodiment, even when the operation of the magnetron 8 is in an unstable critical state, stable and reliable operation can be maintained.

In addition, in Fig. 2, the signals (3) and (4) may be generated as signals of opposite polarity, but in this case, the signal (4) is synchronized with the timing when going from O to 1, and the next ON signal is generated. to occur.

Example 2 Another embodiment will be explained with reference to FIGS. 3 and 4.

In the switching power supply device shown in FIG. 3, the voltage detection means has been changed compared to the circuit shown in FIG. . This transformer voltage detection winding 16d is 1
The number of turns is set to be smaller than that of the next turn yA6a, so that the generated voltage is reduced and sent to the on/off control circuit 3.

By doing so, components with low breakdown voltage can be used in the on/off control circuit 3, and costs can be reduced. The on/off control circuit 3 is configured to delay the detected voltage and then compare it with a predetermined value to obtain the on-start timing.

Next, the operation of the circuit configured as described above will be explained with reference to FIG. (1) in FIG. 4 shows the switching circuit current, (2) shows the switching circuit voltage, and (3) shows the detected voltage generated in the transformer voltage detection winding 6d.
) shows a signal obtained by delaying the above-mentioned detection voltage by a time τ, and (5) in the figure shows a drive signal for controlling the switching circuit 4, respectively.

First, the detection voltage obtained from the transformer voltage detection winding 6d will be explained. The voltage generated here is the voltage generated in the primary winding 6a of the step-up transformer 6 reduced by the turns ratio, and has the same waveform as the switching circuit voltage shown in FIG. 4 (2). As shown in (3), the AC waveform is centered around the 0 level. Since there is a difference of time τ between the timing at which this AC waveform crosses the 0 level and the timing at which the switching circuit voltage crosses the 0 level, this detected voltage is delayed by the time τ as shown in Figure 4 (4). ), and the next ON signal is generated in synchronization with the timing at which the delayed detection voltage (4) crosses the 0 level from positive to negative.

In addition, in FIG. 4, the voltages (3) and (4) may be used with opposite polarities. However, in this case, the next ON signal is generated in synchronization with the timing when the detection voltage (4) crosses the 0 level from negative to positive.

An example of such an operation will be explained in a fourth embodiment.

In this embodiment as well, even if the resonance effect is disturbed and the switching circuit voltage does not reach the θ level as at time t4, stable and reliable switching operation can be maintained.

Embodiment 3 This embodiment is an example in which the transformer voltage detection winding 6d described in Embodiment 2 is utilized more effectively. This embodiment will be explained with reference to FIG.

The switching power supply shown in FIG. 5 is obtained by adding an auxiliary power supply forming circuit 9 to the circuit shown in FIG. Since the on/off control circuit 3 for driving the switching circuit 4 is composed of electronic components, an auxiliary power source of about 5V to 20V is usually required to operate the on/off control circuit 3. . As means for forming this auxiliary power source, this embodiment is provided with an auxiliary IS forming circuit 9 for using the AC voltage generated in the transformer voltage detection winding 6d as an auxiliary power source. In other words, the transformer voltage detection winding 6d
In this embodiment, the auxiliary voltage source is also used as a step-down winding for source formation.

Note that the operation of the circuit shown in FIG. 5 is the same as that explained using FIG. 4 in the second embodiment, so the explanation thereof will be omitted.

Embodiment 4 Next, the specific circuit and its operation of the embodiment are shown in FIGS. 6 and 7.
This will be explained using figures.

In the circuit configuration shown in FIG. 5, the switching power supply device shown in FIG. 6 has the on/off control circuit 3 as a resistor 3a,
Capacitor 3b, monostable multivibrator 3C,
The switching circuit 4 is composed of a switching transistor 4a and a damper diode 4b, and the auxiliary power supply forming circuit 9 is composed of a diode 9.
a and a capacitor 9b.

The operation of the circuit configured in this way will be explained using FIG. 7. Note that in this embodiment, the detection voltage and the delayed detection voltage are of opposite polarity to those of the above-mentioned embodiments 2 and 3.
This is to prevent the resonance action of the main circuit from being disturbed by the influence of the auxiliary power supply formation circuit 9, so the polarity shown in Figure 4 is used as long as it does not damage the resonance conditions of the main circuit. You may.

First, (1) in Figure 7 shows the switching circuit current.
2) shows the switching circuit voltage, (3) shows the auxiliary power supply voltage, the dotted line shows the detection voltage, (4) shows the delayed detection voltage, and (5) shows the drive signal. show.

The auxiliary power supply voltage shown in (3) in the figure is obtained by rectifying the AC voltage generated from the transformer voltage detection winding 6d with a diode 9a and smoothing it with a capacitor 9b. supply. Although the auxiliary power supply forming circuit 9 is shown as a half-wave rectification system, other rectification systems may be used. On the other hand, the AC voltage generated in the transformer voltage detection winding 6d is delayed by the time τ in the on/off control circuit 3 by the resistor 3a and capacitor 3b, as shown in (4). Note that this delay circuit uses inductance and capacitor,
Other formats, such as those using active circuits, may also be used. The delayed detection voltage is then connected to the A terminal of the monostable multi-bibreak 3C. Here, the operation of the monostable multi-bibreak 3C will be briefly explained. The A terminal of the monostable multi-bi break 3C is on the positive edge,
The B terminal starts oscillating operation in synchronization with the negative edge.

Further, the Q terminal generates an output pulse in the positive direction, and the Tsuta terminal generates an output pulse in the negative direction. Now, when the detection voltage as shown in Fig. 7 (4) enters the A terminal of the monostable multivibrator 3C, the monostable multivibrator is activated at the A terminal in synchronization with the positive edge, that is, at timings t2 and t4. 3C
It oscillates with a pulse width determined within, and its output is generated at the Q terminal. This corresponds to the drive signal in FIG. 7(5).

This drive signal is then sent to the next-stage drive circuit 3d, where the current or voltage is amplified so that the switching transistor 4a can be safely driven. Although the switching circuit 4 is shown with a switching transistor 4a and a damper diode 4b, other switching elements such as a field effect transistor (FET), a thyristor, or a gate turn-off thyristor (GTO) may be used instead of the switching transistor. However, if a reverse conducting element is used, the damper diode 4b can be omitted.

In this embodiment, the detection voltage is delayed to cause the monostable multivibrator 3C to oscillate, but the detection voltage directly triggers the monostable multivibrator 3C and the drive signal obtained is delayed and the switching circuit 4 A similar effect can be obtained by applying it to

Embodiment 5 In the above-mentioned embodiment, a delay circuit is used as a correction means from the time when the detection voltage of the transformer becomes O level to the time when the switching circuit voltage becomes 0 level.This embodiment uses the delay circuit of this delay circuit. The time is changed according to the input voltage of the switching power supply device.

First, the necessity of changing the delay time will be explained with reference to FIG. FIG. 8 shows switching circuit voltage waveforms, where (1) in the figure shows a case where the input voltage of the switching power supply is relatively low, and (2) in the figure shows a case where it is relatively high.

When the input voltage is relatively low, the period of the oscillating waveform of the switching circuit voltage is a little long, and when the input voltage is relatively high, the period of the oscillating waveform is a little short. Here, the times from when the detection voltage reaches the O level until the switching circuit voltage reaches the θ level are represented by τ and τ2, respectively, and the relationship is as follows: τ1>τ2. Therefore, this embodiment corrects this timing shift. This embodiment will be explained using FIG. 9. FIG. 9 shows a circuit in which a delay time control circuit 11 is added to the circuit shown in FIG. As the input voltage increases in this circuit, the collector current of the transistor lla in the delay time control circuit 11 increases, and the delayed detection voltage shown in FIG. 7 (4) generally moves upward. Corrected to shift level. Then, the timing at which this voltage crosses the O level becomes earlier than before the correction, and it is possible to generate an on signal earlier.

In this way, in this embodiment, even if the period of the oscillating voltage applied to the switching circuit 4 changes due to a change in the input voltage, a more stable and reliable switching operation can be achieved by providing a corresponding delay time. Can be done.

Note that such delay time correction is also effective when controlling the timing by delaying the drive signal.

In each of the embodiments described above, the load is a magnetron that operates irregularly in a critical state, but it goes without saying that the present switching power supply device can also be used for loads other than magnetrons.

〔Effect of the invention〕

As described above, the switching electric 'a device according to the present invention has the following features:
Even if the load operates irregularly, the switching circuit can be stably controlled on and off.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the first embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of FIG. 1, FIG. 3 is a block diagram of the second embodiment of the present invention, and FIG. Figure 5 is a block diagram of the third embodiment of the present invention, Figure 6 is a specific circuit diagram of the fourth embodiment of the present invention, and Figure 7 is the operation of Figure 6. An explanatory diagram, FIG. 8 is an explanatory diagram of the fifth embodiment of the present invention, FIG. 9 is a circuit diagram of the fifth embodiment of the present invention, and FIG. 10 is a circuit of a general voltage resonant switching power supply device. Fig. 11 is an explanatory diagram of the operation of Fig. 10, Fig. 12 is a circuit diagram of a general switching power supply device with the magnetron as a load in Fig. 10, and Fig. 13 is an explanatory diagram of the operation of the magnetron of Fig. 12. ,
FIG. 14 is an explanatory diagram of the operation of the switching power supply device of FIG. 12. １・・・・・・・・・DC power supply, ２・・・・・・・・・
Transformer voltage detection circuit, 3...On/off control circuit, 4...Switching circuit,
5...Resonance capacitor, 6...
...Step-up transformer, 8...Magnetron, 6d...Transformer voltage detection winding. Figure 1 I: Direct: A power supply 2: Transformer: E&,: tω word 3, 5.
・On/off lIJmn connection 4 ... switch angle °° [ii] wr5...
... 11 voltage transformer Fig. 2 Fig. 3 Fig. 4 Fig. 5 + Town 1117 Fig. 7 Fig. 8') Fig. 9 Fig. 10 Fig. 11 for r+ t2 t3
t4 rs @ Fig. 12 Fig. 13 Fig. 11 Anterior ramus -→-μ 1 gara-1 piece each (relaxed.

Claims (1)

[Claims] 1. A DC power supply, a series circuit of a primary winding of a transformer connected to the DC power supply, and a switching element, a resonance capacitor connected in parallel with the switching element, and the switching element. In a switching power supply device equipped with a control circuit that controls on/off the control circuit, the control circuit includes:
transformer voltage detection means for detecting a voltage induced in the primary winding of the transformer; and a transformer voltage detection means for detecting a voltage induced in the primary winding of the transformer; a determining means for determining when the oscillating voltage reaches a predetermined set value in a region where an oscillating voltage having a polarity opposite to the conduction polarity of the switching element induced by the switching element changes toward the conduction polarity of the switching element; A switching power supply device comprising a discrimination signal delaying means for delaying a discrimination signal outputted from the discrimination means to generate an ON start signal for the switching element. 2. The switching power supply device according to claim 1, wherein the transformer voltage detection means includes a voltage detection winding provided in the transformer. 3. The switching power supply device according to claim 2, wherein the voltage detection winding supplies a power supply voltage to the control circuit. 4. The switching power supply device according to claim 1, wherein the discrimination signal delay means changes its delay time according to the magnitude of the DC power supply voltage. 5. The switching power supply device according to claim 1, wherein the output winding of the transformer is connected to a magnetron via a rectifier circuit. 6. On/off control of a DC power supply, a DC circuit of a primary winding of a transformer connected to this DC power supply, a switching element, a resonance capacitor connected in parallel with the switching element, and the switching element. In a switching power supply device including a control circuit, the control circuit includes:
transformer voltage detection means for detecting a voltage induced in the primary winding of the transformer; detection voltage delay means for delaying a detected voltage output from the transformer voltage detection means; The delayed detection voltage output from the detection voltage delay means in a region where an oscillating voltage of opposite polarity to the conduction polarity of the switching element induced in the primary winding of the switching element changes toward the conduction polarity of the switching element. 1. A switching power supply device, comprising: on-signal generation means for detecting that the voltage reaches a predetermined voltage value and generating an on-start signal for the switching element. 7. The switching power supply device according to claim 6, wherein the transformer voltage detection means includes a voltage detection winding provided in the transformer. 8. The switching power supply device according to claim 7, wherein the voltage detection winding supplies a power supply voltage to the control circuit. 9. The switching power supply device according to claim 6, wherein the detected voltage delay means changes its delay time depending on the magnitude of the DC power supply voltage. 10. The switching power supply device according to claim 6, wherein the output winding of the transformer is connected to a magnetron via a rectifier circuit.