JP3400425B2 - Chopper type switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [0001] The present invention relates to a secondary side of a transformer.
To obtain the desired output voltage by the chopper circuit
Chopper type switching power supply device. [0002] Generally, this kind of cho
The switching power supply unit is especially separated from each output terminal.
Widely applicable to multi-output power supply that can take out various output voltages
Is done. FIG. 7 shows such a chopper type switching power supply.
1 is a circuit diagram showing an example of a device, where 1 is a primary side and a secondary side
Transformer that insulates the transistor, 2 is a transistor or MOS type F
The main switching element made of ET etc.
1 and the main switching element 2 form the inverter circuit 3
Be composed. And the main switching element 2 is switched
The primary winding 1A of the transformer 1
DC input voltage Vin of the inverter circuit 3 is intermittently applied.
You. On the other hand, the secondary winding 1B of the transformer 1 has
Current diode 4, flywheel diode 5, cho
Chopper consisting of coil 6 and smoothing capacitor 7
The rectifying / smoothing circuit 8 on the input side and a PNP transistor.
Switching element 9, flywheel diode 10,
A choke having a choke coil 11 and a smoothing capacitor 12
The tapper circuits 13 are connected in order. 14 is smoothing condensation
Detection level of DC output voltage Vo generated between both ends of
Of the drive pulse supplied to the switching element 9 according to
A control circuit that controls the conduction width.
Vo is stabilized. It is not shown here.
, But the secondary windings 1C of the other transformers 1
A flow smoothing circuit 8, a chopper circuit 13 and a control circuit 14 are provided.
In addition, each output voltage is stabilized. When the main switching element 9 is turned on,
The DC input voltage Vin is the primary winding 1A of the transformer 1.
Is applied to the dot side terminal of the secondary winding 1B.
A positive voltage is induced in the rectifier diode 4 to turn on,
The flywheel diode 5 turns off. This allows
Rectifying diode 4
Through the choke coil 6 and the smoothing capacitor 7
It is. On the other hand, when the main switching element 2 is turned off,
Diode 4 is off, flywheel diode 5 is off
On. As a result, the choke coil 6 is stored until then.
Releases energy that has been used, and tilts linearly with time
The decreasing current flows through the flywheel diode 5
It flows to the yoke coil 6 and the smoothing capacitor 7. like this
The voltage induced in the secondary winding 1B is
Is rectified and smoothed by the DC voltage supplied to the chopper circuit 13.
Is applied. The chopper circuit 13 has a high DC output voltage Vo.
The pulse conduction width to the switching element 9 is increased.
When the DC output voltage Vo is low, the switching element
The pulse conduction width to the element 9 is reduced,
The DC voltage is converted into a rectangular wave. Choke this square wave
Rectifying and smoothing by coil 11 and smoothing capacitor 12
Thus, a desired DC output voltage Vo is obtained. Incidentally, the secondary of the transformer 1 as described above
Type switching power supply with chopper circuit on the side
In the device, the voltage generated in the secondary winding 1B is
Directly with a smoothing filter consisting of
Since it is smoothed to the current voltage and applied to the chopper circuit 13,
Choke coil 11 and smoothing capacitor at the subsequent stage
I have to provide a two-stage smoothing filter together with 12.
Was. This leads to increased costs and power supply equipment.
There was a problem that the size of the device could not be reduced. Therefore, the present invention solves the above problems,
Configure the smoothing filter on the secondary side of the transformer in one stage
In addition, the output voltage can be stabilized.Chot
The purpose is to provide a switching power supply
I do. [0008] SUMMARY OF THE INVENTION A chopper type switch according to the present invention.
In order to achieve the above object,Lord
By switching the switching element,
When the DC input voltage is intermittently applied to the primary winding of the
In addition,Equipped with a switching element in the secondary winding of the transformer
Connected to the switching element
Loose signal widthWith PWM control circuitBy controlling,
Chopper type switching power supply for stabilizing the input voltage
, The PWM control circuit generates a signal between the secondary windings.
Switching at the timing when the generated voltage switches
Turn on the device,Fixed on / off timing
OFF timing of the main switching element driven by
Earlier than in advance,Voltage level generated between the secondary windings
Turning off the switching element according to
It is characterized by being. According to the above configuration, the switching element is
Synchronized with the switching of the voltage generated in the secondary winding of the lance
Turn on at the right timing
No need to provide a smoothing filter on the input side of the
Also ensure that the secondary winding supplies energy to the load.
It becomes possible. Therefore, on the secondary side of the transformer
A certain smoothing filter can be configured in one stage, and cost
And the size of the power supply device can be reduced. Ma
Depending on the voltage level generated between the secondary windings of the transformer.
hand,Main switch driven with fixed ON / OFF timing
Earlier than the off timing of the switching element,This voltage level
When the switching element is turned off when the bell is high
If the voltage level is low, the switch
The turn-off time of the switching element is shortened,
It is possible to stabilize the force voltage. [0010] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Of each embodiment of the chopper type switching power supply in
I will tell. The same parts as in the conventional example are denoted by the same reference numerals,
The description of the common part will be omitted because it is duplicated. FIGS. 1 and 2 show a first embodiment of the present invention.
FIG. 1 shows the overall configuration of the power supply device.
And the switching element 9 constituting the chopper circuit 13
Is connected to one end (dot side terminal) of the secondary winding 1B of the transformer 1
A current detector is provided between the rectifier diode 4 and the anode.
All of the resistors 21 are inserted and connected in a series circuit. Ma
22 is output to the dot side terminal of the secondary winding 1B of the transformer 1.
Synchronous circuit that outputs a signal synchronized with the generated positive voltage
The synchronization signal from the synchronization circuit 22 is
PWM (pulse width) control circuit for controlling the pulse conduction width of the child 9
It is sent out to road 23. Also, the output voltage of the DC output voltage Vo is
The voltage level generated in the secondary winding 1B is
To monitor, resistors 26 and 27 as output voltage detection circuit
Are connected in series from the connection point of the resistors 26 and 27.
The voltage detection signal obtained by dividing the current output voltage Vo is a PWM control circuit.
It is sent to the road 23. And here
Means that the dot side terminal of the secondary winding 1B of the transformer 1 has a positive polarity
When it starts up, the switching element is synchronized with the synchronization signal.
A pulse signal of ON is supplied to the secondary winding 9 and then the secondary winding
1B at a timing corresponding to the voltage level generated.
To supply an ON trigger signal to the switching element 9.
You. Specifically, when the main switching element 2 is turned on, the secondary
If the voltage level generated between windings 1B is low, switch
The on-time of the switching element 9 and, conversely, the main switching element.
The voltage level generated between the secondary windings 1B when the child 2 is on is
If it is high, the off time of the switching element 9 is extended,
Stabilizes the output voltage Vo across the load
You. In 24, an overcurrent flows on the secondary side of the transformer 1.
Overcurrent protection circuit to prevent current
The resistor 21 is provided as a
Current on the secondary side of load 1 has increased beyond
Switching element, the PWM control circuit 23
Intermittently minimizes the pulse conduction width of the drive signal to the child 9
It is configured to perform an oscillating operation. And the second volume
Flywheel to the other end of line 1B, that is, the non-dot side terminal
Connect the cathode of diode 5 to this flywheel
The anode between the diode 5 and the rectifier diode is
Connect a flywheel diode 5
It consists of a series circuit of a coil 11 and a smoothing capacitor 12.
A rectifying / smoothing circuit 25 is constructed by connecting a smoothing filter,
The choke coil 6 and the smoothing capacitor 7 in the example
It is unnecessary. In the above configuration, the switching element 9 and
Therefore, here, a MOS FET with good response characteristics is used.
Is preferred. Also, the other secondary windings 1C are similar.
Circuit configuration. The main switching element 2 is
A pulse signal with the same frequency and pulse width
And are driven off. In other words, the main switching element
2 has fixed ON / OFF timing, so the PWM control circuit
The path 23 is an offset of the pulse signal to the switching element 9.
Imming from the off timing of the main switching element
Can also be set earlier in advance. Next, the operation of the above configuration will be described with reference to FIG.
This will be described with reference to waveform diagrams. In FIG. 2,
The upper part is the voltage waveform generated between the secondary windings 1B of the transformer 1.
VM, the lower stage is the switching element 9 from the PWM control circuit 23.
2 shows a voltage waveform Vs of a pulse signal supplied to the power supply. The main switching element 2 is a fixed timing
The on and off are repeated by the voltage, and the voltage waveform VM in FIG.
As shown in FIG.
A positive voltage is applied to the dot side terminal of the secondary winding 1B of the lance 1.
Is induced. At the same time, the synchronous circuit 22
Detects the zero crossing of the voltage generated between B and
The expected signal is output to the PWM control circuit 23. This same
In response to the synchronization signal from the synchronization circuit 22, the PWM control circuit 23
A predetermined time after the zero-crossing is detected by the
When a positive voltage is generated at the dot side terminal of the next winding 1B
At this point, as shown in the voltage waveform Vs of FIG.
An on signal is output to the element 9. This allows the switchon
The switching element 9 is turned on and switched from the secondary winding 1B.
Through the switching element 9, the resistor 21, and the rectifier diode 4.
For the load 11 and the load
Energy is supplied. The PWM control circuit 23 is connected at the connection point between the resistors 26 and 27.
With the obtained voltage detection signal, the voltage waveform Vs shown in FIG.
In accordance with the voltage level generated between the secondary windings 1B
Output an off signal to the switching element 9
You. Thereby, the switching element 9 is turned off,
From the secondary winding 1B to the choke coil 11 and the smoothing capacitor
The supply of energy to the satellite 12 is shut off. In this case, the main
Generated between the secondary windings 1B when the switching element 2 is turned on.
The higher the voltage level, the higher the switching element 9 is turned on.
The interval t1 becomes shorter, and conversely, the voltage generated between the secondary windings 1B
As the level is lower, the ON time t1 of the switching element 9
Becomes longer, and the output voltage Vo is stabilized. On the other hand, during the off period of the main switching element 2,
Is the energy stored in the choke coil 11
Energy is applied to the smoothing condenser through the flywheel diode 5.
Released to densa 12 and load. As described above, according to this embodiment,Main switch
By switching the switching element 2, the transformer
DC input voltage Vin is intermittently applied to one primary winding 1A.
Along withA switching element is connected to the secondary winding 1B of the transformer 1.
The chopper circuit 13 having the switch 9 is connected to the
Control which is a control circuit for controlling the pulse signal width to the switching element 9
By controlling with the circuit 23, the output voltage Vo can be stabilized.
In a chopper-type switching power supply
Of the voltage generated between the secondary windings 1B
Switching element 9 is turned on byFixed
Main switching element driven by ON / OFF timing
Earlier than the off-timing of child 2,This transformer 1
Timing according to voltage level generated between next windings 1B
So that the switching element 9 is turned off by PW
The M control circuit 23 is constituted. By doing so, the switching element 9
Switching of voltage generated in secondary winding 1B of transformer 1
Turns on at the timing synchronized with
A smoothing filter on the input side of the chopper circuit 13
Even if it is not provided, the secondary winding 1B supplies energy to the load.
Can be reliably supplied. Therefore, the tiger
The smoothing filter (choke coil 11) on the secondary side of
And the smoothing capacitor 12) can be configured in one stage.
Cost reduction and downsizing of the power supply unit
it can. Also,Driven with fixed ON / OFF timing
Earlier than the off timing of the main switching element 2
AndVoltage level generated between secondary windings 1B of transformer 1
The switching element when this voltage level is high,
The turn-off time of the child 9 becomes longer, and conversely, the voltage level becomes
If it is low, the switching element 9 is turned off.
And the output voltage Vo is stabilized.
Can be In this embodiment, the switching element 9 is
The flowing current is detected by a resistor 21 which is a current detector, and this current is detected.
When the flow level is higher than a predetermined value, the PWM control circuit 23
Minimum pulse conduction width of drive signal to switching element 9
The overcurrent protection circuit 24 that makes the intermittent oscillation operation
Have. As a result, the main switching element 2 returns
Operate at fixed ON / OFF timing without a circuit
Use the PWM control circuit 23 of the switching element 9
Thus, overcurrent protection can be easily performed. The above configuration is particularly suitable for a multi-output chopper switch.
This is useful in a switching power supply. That is, each secondary
Have the same circuit configuration in the windings 2B, 2C...
Cuts costs and power supplies
Is advanced. Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. The same as in the first embodiment.
The same reference numerals are given to one place, and the description of the common parts is
Omitted because of duplication. In this embodiment, the switching element 9
The secondary winding 1 of the transformer 1
Connect to the negative output voltage line connected to the other end of B
Inserted. Specifically, the resistor 21 is connected to the secondary winding 1B.
And one end of the switching element 9 are connected between
The other end of the switching element 9 and the cascade of the rectifier diode 4
Ends of flywheel diode 5 connected between
Between the smoothing capacitor 12 and the choke coil 11 in series.
Roads are connected. Further, the PWM control circuit 23 has a secondary winding
When the 1B dot side terminal rises to positive polarity,
A pulse signal that turns on the switching element 9 in synchronization with the signal
And then the voltage level generated in the secondary winding 1B is
At the timing corresponding to the dot side terminal of the secondary winding 1B.
While a positive polarity voltage is generated at the switching element,
9 is supplied with an OFF pulse signal. And this
, The secondary winding 1 is turned on when the main switching element 2 is turned on.
If the voltage level generated between B is low,
The ON time of the element 9 is extended, and conversely, the main switching element 2
Voltage level generated between the secondary windings 1B at the time of turning on is high
In this case, the off time of the switching element 9 is extended,
The output voltage Vo between both ends of the load is further stabilized. Next, the operation of the above configuration will be described with reference to FIG.
This will be described with reference to waveform diagrams. In FIG. 4,
The upper part is the voltage waveform generated between the secondary windings 1B of the transformer 1.
VM, the lower stage is the switching element 9 from the PWM control circuit 23.
2 shows a voltage waveform Vs of a pulse signal supplied to the power supply. Also in this embodiment, the main switching element
2 repeatedly turns on and off at fixed timing
As shown in the voltage waveform VM of FIG.
While the element 2 is on, the secondary winding 1B of the transformer 1
A positive-polarity voltage is induced at the G-side terminal. With this,
The synchronizing circuit 22 has a positive polarity generated at the dot side terminal of the secondary winding 1B.
Outputs a signal synchronized with the polarity voltage to the PWM control circuit 23
ing. By the synchronization signal from the synchronization circuit 22, the PWM
The control circuit 23 operates after the synchronization circuit 22 detects a zero cross.
After a fixed time, the positive terminal is connected to the dot side terminal of the secondary winding 1B.
When the voltage is generated, as shown in the voltage waveform Vs in FIG.
Then, an ON signal is output to the switching element 9. to this
As a result, the switching element 9 is turned on, and the secondary winding 1 is turned on.
Energy is supplied to the load from B. The PWM control circuit 23 is connected at the connection point between the resistors 26 and 27.
With the obtained voltage detection signal, the voltage waveform Vs shown in FIG.
In accordance with the voltage level generated between the secondary windings 1B
Output an off signal to the switching element 9
You. Thereby, the switching element 9 is turned off,
From the secondary winding 1B to the choke coil 11 and the smoothing capacitor
The supply of energy to the satellite 12 is shut off. In this case, the main
Generated between the secondary windings 1B when the switching element 2 is turned on.
The higher the voltage level, the higher the switching element 9 is turned on.
The interval t2 becomes shorter, and conversely, the voltage generated between the secondary windings 1B
As the level is lower, the on time t2 of the switching element 9 is higher.
Becomes longer, and the output voltage Vo is stabilized. As described above, also in this embodiment, the transformer 1
Timing at which voltage generated between secondary windings 1B switches
To turn on the switching element 9,Fixed
Main switching element 2 driven at on / off timing
Earlier than the off timing ofSecondary winding of this transformer 1
At the timing according to the voltage level generated between the lines 1B,
PWM control to turn off switching element 9
Since the control circuit 23 is configured, the chopper
Even if the smoothing filter is not provided on the input side of the path 13,
Energy is reliably supplied to the load from the secondary winding 1B.
It becomes possible. Therefore, the secondary side of transformer 1
Filter (choke coil 11 and smoothing filter)
Densers 12) can be configured in one stage, reducing costs
In addition, the size of the power supply device can be reduced. Also,
According to the voltage level generated between the secondary windings 1B of the lance 1
hand,Main switch driven with fixed ON / OFF timing
Earlier than the off timing of the switching element 2,This voltage
When the level is high, the switching element 9 is turned off
When the voltage level is low, the switch
The turn-off time of the switching element 9 is shortened, and
The pressure Vo can be stabilized. Next, based on FIG. 5 and FIG.
A third embodiment will be described. The same as in the first and second embodiments.
The same reference numerals are given to one place, and the description of the common parts is
Omitted because of duplication. In this embodiment, one primary winding 1A and two primary windings 1A
The secondary windings 1B and 1D connected in series to the
And a resistor 21, a connection point between the secondary windings 1B and 1D.
A direct connection comprising a switching element 9 and a choke coil 11
Connect one end of the column circuit. One end of the secondary winding 1B
That is, the anode of the rectifier diode 4A is connected to the dot side terminal.
Connected to the other end of the secondary winding 1B, that is, the non-dot side terminal.
The anode of the rectifier diode 4B is connected to
The cathodes of the diodes 4A and 4B are connected. So
From the connection point of the rectifier diodes 4A and 4B (see FIG.
(Not shown) and one end of the
Negative side output from one end of the coil 11 to the other end of the load
Connect the smoothing capacitor 12 between the power voltage line and rectify
Diodes 4A and 4B and flywheel diode 5
And the choke coil 11 and the smoothing capacitor 12
The flow smoothing circuit 25 is configured. In the present embodiment, the synchronization circuit 22
Positive voltage was induced in the dot side terminal of the next winding 1B
And the non-dot side terminal of the other secondary winding 1D has positive polarity
When the voltage is induced, each rising signal is represented by P
Output to the WM control circuit 23. The PWM control circuit 23 has a secondary
When the dot side terminal of the winding 1B rises to the positive polarity,
ON pulse to the switching element 9 in synchronization with the synchronization signal
Signal, and then the voltage generated on the secondary winding 1B.
At the timing according to the level, the dot side of the secondary winding 1B
Switching occurs while a positive polarity voltage is being generated at the terminal.
While supplying an off pulse signal to the element 9, the secondary winding
When the non-dot side terminal of line 1D rises to positive polarity,
ON pulse to the switching element 9 in synchronization with the synchronization signal
Signal, and then the voltage generated on this secondary winding 1D
At the timing according to the level, the non-dot of the secondary winding 1D
While the positive polarity voltage is being generated at the
This is for supplying an off pulse signal to the switching element 9. So
Also in this case, when the main switching element 2 is turned on, the secondary
When the voltage level generated between the windings 1B and 1D is low,
The ON time of the switching element 9 is extended, and conversely, the main switch
Generated between the secondary windings 1B and 1D when the switching element 2 is turned on.
When the voltage level is high, the switching element 9 is turned off.
The time is extended, thereby reducing the output voltage Vo across the load.
We are trying to stabilize. Next, the operation of the above configuration will be described with reference to FIG.
This will be described with reference to waveform diagrams. In FIG. 6,
The upper stage shows the voltage generated between the secondary windings 1B and 1D of the transformer 1.
Voltage, that is, the connection point of the rectifier diodes 4A and 4B,
The voltage waveform VM generated between the connection points of the next windings 1B and 1D,
The lower stage supplies the switching element 9 from the PWM control circuit 23
5 shows a voltage waveform Vs of a pulse signal to be applied. Also in this embodiment, the main switching element
2 repeatedly turns on and off at fixed timing
As shown in the voltage waveform VM of FIG.
While the element 2 is on, the secondary winding 1B of the transformer 1
A positive voltage is induced at the terminal on the side of the
The subsequent rectifier diode 4A is turned on while the secondary winding
The rectifier diode 4B connected to 1D turns off. Sync times
The path 22 has a positive polarity generated at the dot side terminal of the secondary winding 1B.
A signal synchronized with the voltage is output to the PWM control circuit 23.
You. PWM control is performed by the synchronization signal from the synchronization circuit 22.
In the circuit 23, the synchronous circuit 22 detects the rising of the secondary winding 1B.
A predetermined time after that, to the dot side terminal of the secondary winding 1B.
When a positive voltage is generated, the voltage waveform Vs in FIG.
As shown, an ON signal is output to the switching element 9.
You. Thereby, the switching element 9 is turned on,
Secondary winding 1B → Rectifier diode 4A → Smoothing capacitor 12
→ choke coil 11 → switching element 9 → resistor 21 → two
A current flows through the path of the next winding 1B. The PWM control circuit 23 is connected at the connection point between the resistors 26 and 27.
According to the obtained voltage detection signal, the voltage waveform Vs shown in FIG.
In accordance with the voltage level generated between the secondary windings 1B
Output an off signal to the switching element 9
You. Thereby, the switching element 9 is turned off,
From the secondary winding 1B to the choke coil 11 and the smoothing capacitor
The supply of energy to the satellite 12 is shut off. In this case, the main
Generated between the secondary windings 1B when the switching element 2 is turned on.
The higher the voltage level, the higher the switching element 9 is turned on.
The interval t3 becomes shorter, and conversely, the voltage generated between the secondary windings 1B
As the level is lower, the on-time t3 of the switching element 9 is smaller.
Becomes longer, and the output voltage Vo is stabilized. Thereafter, the main switching element 2 is turned off.
This time, the non-dot side terminal of the secondary winding 1D of the transformer 1
A positive voltage is induced in the secondary winding 1B.
While the current diode 4A is turned off, it is connected to the secondary winding 1D.
The subsequent rectifier diode 4B turns on. Synchronous circuit 22
To the positive voltage generated at the non-dot side terminal of the next winding 1D
The synchronized signal is output to the PWM control circuit 23. this
By the synchronization signal from the synchronization circuit 22, the PWM control circuit 23
After the synchronous circuit 22 detects the rising of the secondary winding 1D
After a predetermined time, the non-dot side terminal of the secondary winding 1D has a positive polarity.
At the time when the voltage of FIG.
Thus, an ON signal is output to the switching element 9. this
As a result, the switching element 9 is turned on again,
Winding 1D → Rectifier diode 4B → Smoothing capacitor 12 → H
Brake coil 11 → switching element 9 → resistor 21 → secondary winding
A current flows through the path of the line 1D, and the choke coil 11 and the flat
Energy is supplied to the load through the
You. The PWM control circuit 23 is connected at the connection point between the resistors 26 and 27.
According to the obtained voltage detection signal, the voltage waveform Vs shown in FIG.
Depending on the voltage level generated between the secondary windings 1D
Output an off signal to the switching element 9
You. Thereby, the switching element 9 is turned off,
From secondary winding 1D to choke coil 11 and smoothing capacitor
The supply of energy to the satellite 12 is shut off. In this case, the main
Generated between the secondary windings 1D when the switching element 2 is turned off
The higher the voltage level, the higher the switching element 9 is turned on.
The interval t4 becomes shorter, and conversely, the voltage generated between the secondary windings 1D
As the level is lower, the ON time t4 of the switching element 9 is smaller.
Becomes longer, and the output voltage Vo is stabilized. As described above, also in this embodiment, the transformer 1
A tie at which the voltage generated between the secondary windings 1B and 1D switches
Switching element 9 is turned on byFixed
Main switching element driven by ON / OFF timing
Earlier than the off-timing of child 2,This transformer 1
A tie according to the voltage level generated between the next windings 1B and 1D
To turn off the switching element 9
Since the PWM control circuit 23 is configured in the
A smoothing filter is provided on the input side of the chopper circuit 13.
Even if there is no energy, the secondary winding 1B can transfer energy to the load.
Indeed, it becomes possible to supply. Therefore, the transformer
The smoothing filter (choke coil 11 and
And smoothing capacitor 12) can be configured in one stage.
Cost and the size of the power supply unit can be reduced.
You. Also, a voltage generated between the secondary windings 1B and 1D of the transformer 1 is generated.
Depending on the voltage levelFixed on / off timing
Off timing of the main switching element 2 driven by
EarlyIf this voltage level is high
The turn-off time of the element 9 becomes longer, and conversely, the voltage level
Is low, the turn-off time of the switching element 9
Is shortened, thereby stabilizing the output voltage Vo.
Can be. In the present embodiment, in particular, the two secondary windings 1
B, 1D when the main switching element 2 is on and off
, The switch is switched by the synchronization signal from the synchronization circuit 22.
Since the switching element 9 is turned on, the first embodiment and the
Switching at twice the frequency as compared with the circuit configuration of the second embodiment
The switching element 9 can be operated. Therefore, Sui
As the frequency of the switching element 9 increases, the smoothing filter
The choke coil 11 and the smoothing capacitor 12
Can be typed. In addition, the main switching element 2
At turn-on and turn-off, the secondary winding 1
When the B and 1D voltages are switched, the voltage waveform V shown in FIG.
As shown in M, noise occurs when both voltages switch.
However, as in this embodiment, it is easy to
The PWM control circuit 23 is turned on so that the switching element 9 is turned off.
With this configuration, the time during which the voltages of the secondary windings 1B and 1D are switched
Send energy from secondary windings 1B and 1D to the belt
Can be cut off by switching element 9 and affected by leakage
Can suppress the generation of noise. The present invention is not limited to the above embodiment.
Various modifications are possible within the scope of the present invention.
Noh. [0039] According to the present invention, chopper type switching is performed.
Power supply allows smoothing filter on the secondary side of the transformer
Can be configured in one stage, stabilizing the output voltage.
Can be achieved.

[Brief description of the drawings] FIG. 1 shows a configuration of a power supply device according to a first embodiment of the present invention.
FIG. FIG. 2 shows a voltage generated in a secondary winding of
FIG. 5 is a waveform diagram showing a voltage of a pulse signal to the switching element.
You. FIG. 3 is a chopper type switch showing a second embodiment of the present invention.
FIG. 2 is a circuit diagram illustrating a configuration of a switching power supply device. FIG. 4 shows a voltage generated in a secondary winding of the transformer,
FIG. 5 is a waveform diagram showing a voltage of a pulse signal to the switching element.
You. FIG. 5 is a chopper switch showing a third embodiment of the present invention.
FIG. 2 is a circuit diagram illustrating a configuration of a switching power supply device. FIG. 6 shows a voltage generated in a secondary winding of the transformer,
FIG. 5 is a waveform diagram showing a voltage of a pulse signal to the switching element.
You. FIG. 7 is a chopper type switching power supply device showing a conventional example.
FIG. [Explanation of symbols] 1 transformer1A primary winding 1B, 1D secondary winding2 Main switching element 9 Switching element 23 PWM control circuit (control circuit)

Claims (1)

(57) [Claims] [Claim 1] Switching of a main switching element
The DC input voltage is intermittently applied to the primary winding of the transformer
And applies a manner to connect the chopper circuit having a switching element to the secondary winding of the transformer, by controlling the pulse signal width to the switching element in the PWM control circuit, stabilizing the output voltage In the chopper type switching power supply device, the PWM control circuit turns on the switching element at a timing when a voltage generated between the secondary windings switches, and fixes the fixed switching element.
The main switching element driven at the
A chopper-type switching power supply device characterized in that the switching element is turned off in accordance with a voltage level generated between the secondary windings earlier than an off timing of a child .