JPH0638516A - Power supply - Google Patents

Abstract

PURPOSE:To reduce the heat generation of a resistor, etc., and reduce the loss of a circuit at large. CONSTITUTION:A feedback circuit comprising a rectifying diode D2, a switching element S2, and a snubber circuit R1 is constituted, which connect a switching element S1 and a capacitor C1 for smoothing. The leakage energy of an autotransformer T is fed back to the capacitor C1 by turning on the switching element S2 right before the switching element S1 is turned off. Moreover, the switching element S3 is turned off at the same time with the turn off of the switching element S1 so as to prevent a current from returning to an inductance L1 when the switching element S2 is closed to form a feedback circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device using a chopper circuit.

[0002]

2. Description of the Related Art A conventional power supply device is shown in FIG. The smoothing capacitor C ₁ is connected to both ends of the DC power source 1, and one end of the inductance L ₁ of the autotransformer T is connected to the positive terminal of the capacitor C ₁ . A snubber circuit including an inductance L ₂ , a switching element S ₁ , a resistor R ₁ and a capacitor C ₃ is connected to the other end of the inductance L ₁ .

A rectifying diode D ₁ and a smoothing capacitor C are provided on the other end side of the inductance L ₂ of the autotransformer T.
₂ is connected to supply power to the load 2. Next, the operation will be described. While the switching element S ₁ is turned on, the current I _L1 is the inductance L ₁ from the power supply 1, through the switching element S ₁ flows in a waveform as shown in FIG. 8 (a), the magnetic flux in the inductor L ₁ Energy is stored.

Here, FIG. 8B shows the switching element S.
₁ shows the voltage waveform applied, and FIG. 8 (c) shows the current waveform flowing through the inductance L ₂ . Next, when the switching element S ₁ is turned off, the magnetic flux energy stored in the inductance L ₁ serves as a power source, and the diode D ₁ is generated at a voltage proportional to the number of turns of the inductances L ₁ and L _2.
Through which the capacitor C ₂ is charged.

However, at the moment when the switching element S ₁ is turned off, there is no escape for the energy accumulated in the leakage inductance between the inductances L ₁ and L ₂ , and an excessive voltage is applied to the switching element S ₁ at the moment. In order to prevent this, conventionally, a snubber circuit composed of a resistor R ₁ and a capacitor C ₃ is used, and the energy stored in the leakage inductance is consumed by the resistor R ₁ and stored in the capacitor C _3. Therefore, the breakdown voltage of the switching element S ₁ is prevented from being exceeded.

[0006]

However, in the conventional method using the snubber circuit, all the energy of the leakage inductance is consumed by the resistor R ₁ , and the electric charge stored in the capacitor C ₃ is changed to the switching element S ₁ There to be emitted through the resistor R ₁ at the moment of oN resistance will flow current by leakage is twice the R _1, therefore, the heat generation increased resistance R _1, referred to greater loss of the entire circuit problem was there.

The present invention has been made in view of the above points, and provides a power supply apparatus for reducing heat generation such as resistance and loss of the entire circuit.

[0008]

The present invention comprises a smoothing capacitor connected to the power source side, and a chopper circuit configured by an autotransformer and a first switching element to supply power to the load side. In a power supply device, a second switching device in which the first switching element and the capacitor are connected in parallel.
A series circuit of switching element and snubber resistance of
A control means for turning on the second switching element immediately before the first switching element is turned off is provided.

According to a second aspect of the present invention, a third switching element is provided between the smoothing capacitor and the power source, the second switching element is turned on immediately before the first switching element is turned off, and the third switching element is turned on. Means for turning off the switching element at the same time as the first switching element, turning off the second switching element before turning on the first switching element, and turning on the third switching element at the same time as the first switching element Is provided.

[0010]

By turning on the second switching element immediately before turning off the first switching element, the first switching element is turned on.
The energy stored in the leakage inductance of the autotransformer generated at the moment when the switching element of is turned off is returned to the smoothing capacitor via the snubber resistor. Therefore, the leakage energy of the autotransformer must be reused. Therefore, it is possible to reduce the loss of the entire circuit and heat generation of the snubber resistance.

Further, in the second aspect, as in the first aspect, the energy stored in the leakage inductance of the auto transformer generated at the moment when the first switching element is turned off is smoothed via the snubber resistor. It is possible to reuse the leakage energy of the autotransformer by returning the leakage energy to the capacitor for use in the circuit, so that the loss of the entire circuit and the heat generation of the snubber resistor can be reduced. In addition, when the second switching element is turned on to form the feedback circuit to feed back the leakage energy to the smoothing capacitor, the third switching element is turned off at the same time as the first switching element.
It is possible to prevent the current from returning to the auto transformer.

[0012]

Embodiments of the present invention will now be described with reference to the drawings.
To do. FIG. 1 shows an overall block diagram, and FIG. 3 shows a specific circuit.
The figure is shown. The difference from the previous example is that the resistance R₁,
Capacitor C₃Instead of a snubber circuit consisting of
Itching element S₁And smoothing capacitor C₁And are connected in parallel
Continued rectifier diode D₂, Switching element S ₂,
Snubber resistance R₁By constructing a feedback circuit consisting of
It

Further, in order to feed back the leakage energy to the capacitor C ₁ , when the switching device S ₂ is closed to form a feedback circuit, the switching device S ₃ for preventing the current from returning to the inductance L ₁ is connected to the capacitor. It is configured to be connected in series between C ₁ and the power supply 1. In FIG. 1, the control circuit 3 includes a switching element S.
₁ performs pulse width control, and the PWM signal controls the switching element S ₃ to be turned on and off via the drive circuit 6. Further, the PWM signal from the control circuit 3 is input to the drive circuit 5 via the delay circuit 4, and the drive circuit 5 forms a switching element S that forms a feedback circuit.
₂ is on / off controlled.

The control circuit 3, as shown in FIG.
It is composed of an R oscillation circuit 31 and a comparator 32, and the divided voltage of the resistors R ₂ , R ₃ and R ₄ connected to the output side is input to the comparator 32. Then, as shown in FIG. 4A, the triangular wave from the CR oscillation circuit 31 and the divided voltage are compared by the comparator 32 to determine the on-duty, and the PWM as shown in FIG.
Generating a control signal.

The delay circuit 4 has, for example, a 4-stage buffer structure, and the drive circuits 5 and 6 are transformers T.
₁ and T ₂ have the same configuration. Next, the operation will be described with reference to FIGS. FIG. 2 shows an operation waveform diagram, (a) shows the voltage waveform of the switching element S ₁ ,
(B) shows the current I _L1 flowing through the inductance L ₁ ,
(C) shows the voltage waveform of the switching element S ₂ , and (d) shows the voltage waveform of the switching element S ₃ .

In the initial state, the switching element S
₁, S₂, S₃Both are off. Next, FIG.
As shown in (a), the switching element S₁Is on
Switching element S₂Is turned on by delay circuit 4
As shown in FIG._dOnly
Itching element S₁Be late from. Also, the switching element
Child S₃Is the switching element S₁It is turned on at the same time (Fig.
2 (d)). At that time, the positive electrode of the power supply 1 → the inductance L
₁→ Switching element S ₁→ Use the negative loop of power supply 1
Flow I_L1Flows, the inductance L₁The magnetic flux energy is
It can be stored.

Next, when the switching element S ₁ is turned off, a current flows from the inductance L ₁ to the inductance L _1.
1 → inductance L ₂ → diode D ₁ → load 2 → ground, and the booster works as a booster so that a voltage boosted by the turns ratio of the inductances L ₁ and L ₂ is applied to the load 2. However, the inductance L ₁
Between L ₂ and L ₂ , there is usually a leakage inductance, and the energy stored here is the switching element S.
Apply transient voltage to ₁ . Therefore, conventionally, had consumed leakage energy in the snubber circuit, in this embodiment, as shown in FIG. 2 (c), by turning on the switching element S ₂ immediately before the switching element S ₁ is turned off, A snubber circuit is formed by the resistor R ₁ and the capacitor C ₁ , the switching element S ₁ is turned off, and the switching element S ₃ is turned off at the same time, and the leakage energy between the inductances L ₁ and L ₂ is fed back to the capacitor C _1. There is.

Next, the switching element S₁Turn on
Before switching element S₂Turn off the switching element
Child S₁, S₃Is turned on, the inductance L₁To
Current I_L1Is the capacitor C₁To prevent it from flowing into
ing. Next, the switching element S₁Just before turning off
And the switching element S₂Turn on. More than
When the operation is repeated, the inductance L₁, L₂Lee between
Cage energy is input Smoothing capacitor C₁Return to
Can and capacitor C ₁The energy returned to
Can be played.

The control circuit 3, the delay circuit 4, the drive circuit
Switching element S on paths 5, 6 etc.₂，₃On, off system
Control the leakage energy of the auto transformer T.
Densa C₁It constitutes the control means for returning to. (Embodiment 2) Embodiment 2 is shown in FIG. In this embodiment, CR
PWM control waveform from the oscillator circuit 31 and the comparator 32
Control circuit 3 being formed and control signal from the control circuit 3
Switching element S₁Send to delayed times
Path 4 and switching element S ₂For making the control waveform of
The detection circuit 7 and the output of the detection circuit 7 are delayed for a predetermined time.
Delay circuit 8 and JK type flip-flops 9 and 10
And the like, and the switching element S₁, S₂, S
₃The configuration such as is similar to that of the previous embodiment.

Next, the operation of this embodiment will be described with reference to the operation waveform chart of FIG. In this embodiment, the timing of the current flowing through the switching elements S ₁ and S ₃ and the inductance L ₁ is the same as the operation timing of the first embodiment shown in FIG. The difference between the previous embodiment, the on-switching element S _2, the timing of the off only when the drain-source voltage V _DS of the switching element S ₁ is excessive, it has to be turned on the switching element S ₂ It is in.

The operation of the switching element S ₂ will be described in detail below. A waveform obtained by delaying the control waveform A ₀ of the control circuit 3 that creates the PWM control waveform by the output voltage detection by the CR oscillation circuit 31 and the comparator 32 by T _d1 through the delay circuit 4 is used as the gate waveforms of the switching elements S ₁ and S ₃ . The switching elements S ₁ and S ₃ are switched by the waveform of the output T ₁ of the delay circuit 4 as shown in FIG.

On the other hand, the switching of the switching element S ₂ is determined by the following logic circuit. That is,
Drain-source voltage V of switching element S ₁
A value obtained by dividing _DS by resistors R ₇ and R ₈ and a reference value V ₁ formed by resistors R ₅ and R _{6 of the} detection circuit 7 are compared by a comparator 71, and from this detection circuit 7, the switching element is switched. The waveform A ₂ that is set to the H level is output only when the drain-source voltage V _{DS of} S ₁ is higher than the reference value V ₁ .

Waveform A₂Is the switching element S₁The drain
In-source voltage V_DSIs the reference value V ₁While higher than (T
_VS1), That is, the switching element S₂Resistance by
R₁, Capacitor C₁The feedback circuit of the leakage energy
Is a signal that goes to H level while it is being fed back.
And the switching element S₂Is at least on during this time
It must be.

However, when it is not necessary otherwise, it is better to turn off the switching element S ₂ in terms of malfunction. Therefore, it is necessary to have a waveform that has a certain margin before and after the period T _VS1 and that is long and short in proportion to the time during which the feedback circuit by the switching element S ₂ operates. The waveform is formed by a logic circuit as follows. That is, a waveform A ₃ which is the inverted waveform A ₂ is formed by the inverter G ₁ , and a waveform A ₄ which is the logical sum of the waveform T ₂ and the waveform A _{3 obtained by} delaying the waveform A ₃ by the delay circuit 8 by the time T _d2 is OR gate G. ₂
To form.

The flip-flop 9 which performs a toggle operation is triggered by the fall of the waveform A ₄ to form the waveform J ₁ . This waveform J ₁ and the output waveform A _{0 of the} control circuit 3
And are logically output by the NOR gate G ₃ , a waveform A ₅ is formed, and a toggle waveform J ₂ is obtained by the flip-flop 10 triggered by the rising of the waveform A ₅ . This J
The waveform of ₂ is H just before the switching element S ₁ is turned off.
The signal becomes the level, and the time becomes longer or shorter in proportion to the period T _VS1 described above, and thus the signal becomes the H level in proportion while the feedback circuit is operating.

This signal J ₂ causes the switching element S
By performing the switching of ₂ , it is possible to form the feedback circuit by turning on the switching element S ₂ only when the feedback circuit is necessary, and it is possible to prevent malfunction of the circuit and the like.

[0027]

As described above, the present invention includes the smoothing capacitor connected to the power source side, and the chopper circuit configured to include the autotransformer and the first switching element to supply power to the load side. In the power supply device, a series circuit of a second switching element and a snubber resistor that connects the first switching element and the capacitor in parallel is provided, and the second switching element is connected immediately before the first switching element is turned off. Since the control means for turning on is provided, by turning on the second switching element immediately before turning off the first switching element, the leakage inductance of the auto transformer generated at the moment when the first switching element turns off. The energy stored in is fed back to the smoothing capacitor via the snubber resistor, and therefore Bets can be reused transformer leakage energy, in which an effect that it is possible to reduce the heat generation of the circuit reduction of the total loss, and the snubber resistor.

According to a second aspect of the present invention, a third switching element is provided between the smoothing capacitor and the power source, the second switching element is turned on immediately before the first switching element is turned off, and the third switching element is turned on. Means for turning off the switching element at the same time as the first switching element, turning off the second switching element before turning on the first switching element, and turning on the third switching element at the same time as the first switching element Since the energy stored in the leakage inductance of the auto transformer generated at the moment when the first switching element is turned off is provided to the smoothing capacitor through the snubber resistor, as in the case of claim 1, By returning, the leakage energy of the auto transformer can be reused, reducing the loss of the entire circuit, and It can be reduced heat generation of the snubber resistor. Further, when the second switching element is turned on to form the feedback circuit to feed back the leakage energy to the smoothing capacitor, the third switching element is turned off at the same time as the first switching element. The current can be prevented from returning to the.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention.

FIG. 2 is an operation waveform diagram of FIG. 1 above.

FIG. 3 is a specific circuit diagram of FIG. 1 above.

FIG. 4 is an operation waveform diagram of the control circuit of the above.

FIG. 5 is a circuit diagram of a second embodiment of the above.

FIG. 6 is an operation waveform diagram of FIG. 5 above.

FIG. 7 is a circuit diagram of a conventional example.

8 is an operation waveform diagram of FIG. 7 of a conventional example.

[Explanation of symbols] 1 power supply 2 load C ₁ smoothing capacitor T auto transformer S ₁ first switching element S ₂ second switching element S ₃ third switching element R ₁ snubber resistance

Claims (2)

[Claims] 1. A power supply device comprising: a smoothing capacitor connected to a power supply side; and a chopper circuit configured by an autotransformer and a first switching element to supply power to a load side. A series circuit of a second switching element and a snubber resistor for connecting the switching element and the capacitor in parallel is provided, and a control means for turning on the second switching element is provided immediately before the first switching element is turned off. Power supply device characterized by. 2. A third switching element is provided between the smoothing capacitor and a power source, and the second switching element is turned on immediately before the first switching element is turned off.
The third switching element turns off at the same time as the first switching element, the second switching element turns off before the first switching element turns on, and the third switching element turns on at the same time as the first switching element. The power supply device according to claim 1, further comprising control means.