JP2003259635A - Switching power circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably start a switching operation when a power source is started, in a compound resonant converter provided with a soft start circuit. <P>SOLUTION: In a soft start circuit, a constitution is provided so as to output a constant voltage control signal for controlling a switching frequency more than necessary only when a switching element is turned on. In this way, in the point of time when the switching element tends to make a transition of turning from off to on, the constant voltage control signal for controlling the switching frequency more than necessary is not outputted so that the switching element can make transition stably from an on-condition to an off-condition. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various electronic devices.
Switching power supply circuit
You. 2. Description of the Related Art In recent years, switches used for electronic equipment have been developed.
For power supply circuits, it is important to reduce noise and power consumption of equipment.
Demand is growing. Therefore, the switching power supply circuit
Resonant type switch
Switching converters are being adopted
You. As such a resonance type switching converter,
A voltage resonant converter with a parallel resonant circuit on the primary side
Are known. This voltage resonance type converter
Compared to the resonant switching converter
Low switching loss in switching element
It is known that such noise reduction and power saving
It is expected to be effective. [0003] By the way, a voltage resonance type converter has a zero current.
The operating range in which pressure switching (ZVS) can be performed is as follows:
The impedance is Zr, the input voltage is Vin, and the load current is Io.
Then, Io ≧ Vin / Zr is given. For this reason, high input voltage and light load
In some areas, ZVS may not be possible,
This has been considered a practical problem. Therefore, the applicant of the present invention, for example, applies a voltage to the primary side.
Equipped with a resonant converter,
With a resonance circuit such as a column resonance circuit or a series resonance circuit,
Switching with a configuration as a complex resonant converter
A power supply circuit has already been proposed and filed. Such a complex
The oscillation switching power supply circuit, as described above,
ZVS is guaranteed by providing a resonant circuit on the
Operating range can be extended. FIG. 5 shows a composite resonance filed by the present applicant.
Switch that can be configured based on a shape converter
2 shows a configuration example of a switching power supply circuit. Power supply shown in this figure
The circuit responds when the main power switch is turned on.
Operate main power supply and turn on / off main power switch
Regardless of off, as long as the commercial AC power supply AC is connected
And a standby power supply that operates constantly. First, the standby power supply will be described.
For the commercial AC power supply AC, the commercial power transformer SBT
Are connected in parallel. Commercial power transformer SB
T is also the secondary winding of the commercial power transformer SBT,
It consists of a bridge rectifier circuit Di1 and a smoothing capacitor Ci1.
Rectifying / smoothing circuit is connected to the smoothing capacitor Ci1.
A rectified smoothed voltage Ei1 as a direct current is obtained. [0007] The three-terminal regulator REG has a rectifying smoothing current.
DC voltage stabilized at the required level by inputting the voltage Ei1
Outputs source voltage Vcc as voltage across capacitor C1
I do. This DC power supply voltage Vcc is
The power is always supplied as the operation power of the data 2. this
Operation control of an electronic device provided with the power supply circuit shown in FIG.
Execute. Also, the DC power supply voltage Vcc is
Then, it is also supplied to the relay RL. This relay RL
The main switching
Provided to control on / off operation of the inverter
You. Next, the main power supply section will be described. May
The microcomputer 2 turns on / off the power supply section.
Drive the power supply RL to connect the commercial AC power supply AC and the main power supply.
Voltage inserted between the line and the bridge rectifier circuit Di
By controlling the on / off of the power switch SW
Is When the main power supply should be turned off
Indicates that the microcomputer 2 has an on / off signal (ON /
OFF) and output the L level. In this case, the tiger
Transistor Q2 is off, and relay RL is also non-conductive.
It is controlled to be in a state. Therefore, the commercial AC power supply A
Main switch SW inserted in C line is off
State. For this reason, the bridge rectifier Di has a commercial exchange.
Current power is not supplied, and the main power supply is turned off. On the other hand, for example, when the main power supply is turned off.
When turning on from the state, the microcomputer 2
Switches the on / off signal (ON / OFF) to H level
You. As a result, the transistor Q2 turns on and conducts.
The relay RL is also turned on, and the main switch S
W turns on. As a result, the commercial AC power supply AC
To be supplied to the bridge rectifier circuit Di on the power supply side.
And the main power supply unit is activated. In the following,
In the case of “power on”, the main switch SW
Turn on and turn on commercial AC power supply AC
Shall be referred to. [0011] Commercial with the main switch SW inserted
The bridge rectifier circuit Di and
The rectifying and smoothing circuit formed by the smoothing capacitor Ci
Connected. With this rectifying and smoothing circuit, a smoothing capacitor
A rectified smoothed voltage Ei is obtained at both ends of Ci, and a switch
Supplied as a DC input voltage to the
It is. The primary-side switching converter has one
Of the so-called sing
Configuration as a voltage-resonant converter using the lu-end method
Has been adopted. The switching element Q1 is connected to a switch described later.
Connected in series with the primary winding N1 of the switching transformer TR1.
Thus, a series connection circuit is formed. And this series connection
Connect the primary winding N1 side of the connection circuit to the DC input voltage line
The switching element Q1 side is connected to the primary side ground.
Continue. Further, for the switching element Q1,
For example, the reverse voltage when the switching element Q1 is turned on.
Damper diodes forming a flow path are connected in parallel.
You. Further, for the switching element Q1, the primary side
The parallel resonance capacitors Cr are connected in parallel. This primary
The side parallel resonance capacitor Cr has its own capacitance and
Leakage of primary winding N1 of switch transformer TR1
A primary parallel resonance circuit is formed by the inductance
You. With this primary side parallel resonance circuit, the voltage resonance type
All switching operations are obtained. The drive circuit 1 includes a switching element Q1
Drive. Also, the feedback from the photocoupler PC
Voltage control signal according to the level of the secondary side DC output voltage Eo
Accordingly, the switching frequency of the switching element Q1 is
By variably controlling the secondary side DC output voltage Eo
Stabilize. The switching transformer TR1 is connected to the primary side.
With the secondary side insulated, switch the primary side switching output to
Transmit to the next side. The structure of this switching transformer TR1
The construction is not shown here, but for example, the core has 2
An EE-type core obtained by combining two E-type cores is used.
Then, the primary winding N1 and the secondary winding N2 are connected in the EE type core.
Winding for independent winding position on the center magnetic leg
I do. Thereby, the primary winding N1 and the secondary winding N2
The required leakage inductance can be obtained.
ing. The secondary of the switching transformer TR1
A secondary parallel resonance capacitor C2 is arranged in parallel with the winding N2.
Connected to a column. As a result, the secondary parallel resonance
The capacitance of the capacitor C2 and the leakage of the secondary winding N2.
The secondary parallel resonance circuit is formed by the
The voltage resonance operation is obtained on the secondary side. in this way
In the circuit shown in FIG.
Primary side parallel resonance to make the operation of the barter a voltage resonance type
Circuit with a secondary parallel resonance circuit on the secondary side.
The configuration as a combined resonance type converter is adopted. this
For example, the voltage at which the secondary parallel resonance circuit is not provided
More power must be supplied to the load than a resonant converter
It has become so. In this case, the secondary winding N2 is not shown.
The rectifier diode Do and the smoothing capacitor Co
Is formed. And this
Due to the operation of the half-wave rectifier circuit, both the smoothing capacitor Co
The secondary DC output voltage Eo is obtained as the terminal voltage. this
The secondary side DC output voltage Eo is controlled by a load as a load (not shown).
Supplied to the road. Next, the configuration for constant voltage control
explain. The secondary side DC output voltage Eo is
Then, the voltage is divided by the voltage detection resistors R1 and R2,
Is input to the load regulator SR. Chantreguille
In the data SR, the anode side is connected to the secondary side ground,
The sword is connected to a DC voltage power supply Vcc via a resistor R10.
Have been. Thereby, the shunt regulator SR
The divided level of the input secondary side DC output voltage Eo and the internal
A constant voltage system that compares with the reference voltage level and indicates the error
Control signal through the photocoupler PC to drive the primary side
Supply to Road 1. In the drive circuit 1, the input constant voltage system
Switching of switching element Q1 based on control signal
The frequency is variably controlled. This allows the secondary DC output
The level of the voltage Eo is variably controlled to achieve a constant voltage.
Will be. By the way, as shown in FIG.
In a switching power supply circuit equipped with an inverter, one switch
The off-period within the switching cycle is
Capacitor Cr, secondary side resonance capacitor, and primary winding N
1. Depending on the leakage inductance of the secondary winding N2
The fixed time is determined. Therefore, the switching frequency
The variable control of the number is the ON period within one switching cycle.
This is done by changing the interval. The constant voltage control signal is actually a photocoupler.
Retraction of shunt regulator SR flowing through PC
Only the current. Therefore, the current level of the constant voltage control signal
Indicates that the secondary side DC output voltage Eo
As the load rises, the load becomes heavy and the secondary DC
It decreases as the output voltage Eo decreases. In the drive circuit 1, a constant voltage control signal is used.
When the current increases, the switching element Q1 is turned off.
The switching frequency by shortening the interval (TOFF)
Control. Also, the current as the constant voltage control signal is
If the number decreases, the OFF period of the switching element Q1 (TOF
F) to increase the switching frequency
Control. Here, the operation of the power supply circuit shown in FIG.
FIG. 6 shows a waveform corresponding to the constant voltage control. In this FIG.
Of the switching frequency control in the power supply circuit shown
For example, when the load becomes light, the
When the pressure Eo increases, the switching frequency is increased.
On the contrary, the load becomes heavy and the secondary side DC output voltage Eo
Is decreased, the control is performed so as to decrease the value. FIG.
(A) The operation waveforms at a light load shown in (b) will be described.
And the voltage Vce across the switching element Q1 is turned on.
During a period TON that is at 0 level, and a period TOF when the device is off
In F, a voltage resonance pulse is obtained as shown in the figure.
Waveform. On the other hand, the switching element Q
The switching current Ic flowing through 1 during the period TON
It flows as a sawtooth wave that changes from negative polarity to positive polarity, and the period T
It becomes 0 level at OFF. Also, under heavy load
Also, the voltage across the switching element Q1 shown in FIG.
Vce provides a resonance pulse voltage during the period TOFF
It becomes a waveform. The switching current shown in FIG.
Ic is negative during turn-on during the on-period,
After that, it flows in reverse to the positive polarity. FIG. 6A corresponding to a light load condition.
FIGS. 6C and 6D corresponding to the waveform of FIG.
When comparing with the waveform of (1), the switching period (TON +
TOFF) is longer at light load than at light load
You can see that. That is, as described above,
Switching frequency as the tendency of heavy load
Is controlled to be lower. Also,
The period TOFF is constant and can be varied for the period TON.
It can also be seen that the switching frequency is variable. The voltage Vc across the switching element Q1
When comparing the peak level Vce-peak of e, light load
It is higher at heavy load than at time. This is an example
For example, in the characteristic diagram of FIG. 7, the load current and the peak voltage Vce
It is also shown as a -peak relationship. In other words, heavy load
As the load current increases, the peak
The peak voltage Vce-peak is high. Also, in FIG.
Is higher at higher input voltages than at lower input voltages.
The peak voltage Vce-peak is also shown to be high.
You. [0025] Here, FIG.
The main switch SW
When the power is turned on when switching from off to on
The operation will be described with reference to the timing chart of FIG.
I will tell. At some point, as shown in FIG.
Microcomputer 2 to turn on the power supply
ON / OFF signal (ON / OFF) output from L level
Assume that the level has been switched from (OFF) to H level (ON). Do
And the relay RL is driven and the main
The switch SW changes from off to on, and the main power supply
The rectifying voltage of the bridge rectifier circuit Di is applied to the smoothing capacitor Ci.
Current flows in and the voltage across the smoothing capacitor Ci is regulated.
Current smoothing voltage Ei rises to a specified level.
You. The switching element Q1 is shown in FIG.
The rectified smoothed voltage Ei (DC input voltage)
Starts switching based on the
Power will be supplied to the secondary side via TR1. However, when starting up the power supply,
Therefore, the secondary side DC output voltage Eo is still on the secondary side.
Not generated. Therefore, the secondary side DC output voltage Eo
Voltage control that flows to the photocoupler PC according to the level of
As shown in FIG. 8B, the current level of the signal
Level continues. In this way, when the power is turned on,
Therefore, the current level of the constant voltage control signal becomes almost 0 level.
You. Therefore, the drive circuit 1 includes the switching element Q
Maximum ON period (TON) of 1 and minimum switching
In this case, the control is performed so as to set the switching frequency. Power supply
When the switching element Q1 is turned on
As the interval (TON) becomes longer, as shown in FIG.
And the switching element Q1 in the ON period (TON)
The amount of current flowing also increases, and accordingly, the main switch
Is excessive as shown in FIG. 8 (b).
I will. And, in some cases, the switching element Q1
State that exceeds the rated voltage of the transistor element as
State, which may lead to element destruction.
Was. Therefore, for the power supply circuit shown in FIG.
Configuration provided with a soft start circuit as shown in FIG.
Can be considered. 9 is the same as FIG.
The same reference numerals are given to parts and the description is omitted here.
You. In FIG. 9, the soft start circuit
Transistors Q3 and Q4, resistor R3, time constant capacitor C3,
And voltage dividing resistors R4-R5 connected in series. Series connection
The connected voltage dividing resistors R4 to R5 are connected as shown in FIG.
On / off signal (O
(N / OFF) line and the primary side ground.
Supports the level obtained by dividing the on / off signal (ON / OFF)
A current to flow through the base of the transistor Q4. Soft star formed by the above element
The operation of the gate circuit will be described with reference to the timing chart of FIG.
explain. For example, when the main switch SW is turned off,
When the power supply is turned off,
Signal (ON / OFF) is at L level (0 level).
Since no base current flows through the transistor Q4, the transistor
Q4 is turned off. On the other hand, the main switch SW
When turning on the main power supply unit by turning on
As shown in FIG. 0 (a), the on / off signal (ON / OFF)
This switches from the L level to the H level. to this
Accordingly, transistor Q4 is turned on, and the time constant
The transistor Q3 connected via the capacitor C3
Source current and turn on transistor Q3 as well.
I do. When the transistor Q3 is turned on, the DC power
Voltage power supply Vcc to resistance R10 → photo of photocoupler PC
Diode → resistance R3 → time constant capacitor C3 → Transient
The path from the collector of the star Q4 to the emitter of the transistor Q4
Current will flow. When the power is turned on, the secondary
Since the side DC output voltage Eo is not generated,
The photo die of the photo coupler PC by the regulator
The current flowing through the Aether cannot be drawn. But
However, in the circuit shown in FIG.
Current flows through the photodiode due to the
And As a result, as shown in FIG.
Even when the power is turned on, the constant voltage
Drive signal (current) through photocoupler PC
It can flow to the road 1. Therefore, the switching element
In the state where Q1 has started the switching operation, FIG.
As shown in (c), the switching frequency is forcibly increased.
Can be done. And even when the power is turned on,
If the switching frequency is controlled to be higher,
The off period of the switching element Q1 is short, and FIG.
(D) and as shown in FIG.
The amount of switching current flowing through the switching element Q1 and the off state (TO
FF) can reduce the voltage Vce generated at both ends.
It works. The collector and transistor of the transistor Q4
Time constant capacitor inserted between base of transistor Q3
C3 keeps the operation of the soft start circuit constant after the power is turned on.
Functions as a timer to stop after a time. Toes
When the soft start circuit starts operating, the time constant
The base current of the transistor Q3 flows through the capacitor C3.
Charging is performed. Thereby, the time constant capacitor C
The potential of 3 gradually increases, but with this,
The base potential of transistor Q3 will decrease.
You. Then, the base potential drops below a certain level.
At this point, the transistor Q3 is turned off. Transistor
When Q3 is turned off, the photocoupler P
Soft-start operation for forcing constant voltage control signal to C
Stops. When the soft start operation stops,
Since the secondary side DC output voltage Eo is obtained,
Based on the level of the side DC output voltage Eo
The constant voltage control circuit system provided with the
U. However, the switching element Q1 is turned off.
If the switching frequency is controlled high by shortening the
That is, the switching element Q1 is turned off from the on state.
It has the function of operating to be in a state. Follow
As described above, the drive circuit
It is said that constant voltage control current is constantly flowing for 1
This means that the switching element Q1 is turned off when the power is turned on.
It is said that the action that tries to make it work continuously
Will be. Therefore, the switching element Q1
The disadvantage of starting the switching operation during the ON period is
The switching element Q1 is turned off
Transition to the power-on state,
Switching element Q1 may not start properly
You will have the problem of squealing. The switching of the switching element Q1
If the start of the switching operation does not go well,
This leads to a delay in the start of the switching operation. FIG.
The soft start circuit shown in Fig.
The current flowing through the photodiode is gradually increased by the time constant.
Since the operation is terminated while lowering,
As the time elapses, the photocoupler PC
The level of the constant voltage control signal input to the live circuit 1 is also low.
Going down. In other words, the switching frequency is
It changes so that it becomes lower as time passes.
Therefore, if the start of switching operation is delayed,
Operation is initiated by the relatively low switching frequency of
Will be. Therefore, compared with the power supply circuit shown in FIG.
Then, the peak voltage Vce- applied to the switching element Q1
Although the peak is suppressed, it is still not enough.
The peak voltage Vce-peak is the rated voltage of the switching element Q1.
There is a possibility that the device will be destroyed due to exceeding
Would. It is also difficult to secure a margin for this.
No. Accordingly, the present invention provides the above
Considering the problems that have been addressed,
To be configured. In other words, rectifying and smoothing by inputting commercial AC power
Rectifying smoothing means for generating a DC input voltage by performing an operation
And a switching element that outputs the DC input voltage intermittently
Switching means formed with
Switching element forming the switching means
It has a driving circuit that operates. In addition, the switch
Insulated type that transmits the switching output from the primary side to the secondary winding
It has a switching transformer. Also, at least,
Leakage inductor of primary winding of switching transformer
And the capacitance of the primary resonance capacitor.
And the operation of the switching means is of a resonance type.
The primary resonance circuit provided as described above is provided. Also, Sui
Leakage inductance of the secondary winding of the switching transformer
And the secondary resonant capacitor connected to this secondary winding.
The secondary side formed by the capacitance of the capacitor
A vibration circuit is provided. It also includes a secondary side resonance circuit.
The alternating current obtained in the secondary winding of the switching transformer
Input voltage and output the secondary side DC output voltage.
And the level of the secondary DC output voltage
A constant voltage control signal corresponding to
The switching frequency of the switching element.
Constant voltage control means for performing variable control. And power on
The switching element is turned on for a certain period after operation.
Period, and only during this detected period
The switching frequency of the switching element is maintained more than required
Output a constant voltage control signal to the drive circuit.
Providing a soft-start circuit adapted to
did. The switching power supply circuit having the above configuration is
By adopting a configuration as a so-called composite resonant converter,
In addition, the output of the secondary side is stabilized by switching frequency control.
It is made to try to change. And such a switchon
Excessive current and voltage generated at startup for the power supply circuit
Soft start circuit to protect the switching element from
Provided. The soft start circuit according to the present invention
Switching frequency is higher than required for a certain period of time
So that the switching element
The amount of current flowing through the
Be controlled. And the switching frequency
The switching element is turned on to control more than necessary
Only when the switching frequency is lower than required.
Output a constant voltage control signal to control
ing. This is, in other words, whether the switching element is off.
At the point when the switching frequency
The constant voltage control signal to control the number
It will not be. This allows the switching element
Enables stable transition from ON state to OFF state
It will work. FIG. 1 shows an embodiment of the present invention.
2 shows a configuration example of all switching power supply circuits. this
The power supply circuit shown in the figure has one switching element.
A so-called single bridge voltage resonance type converter
Data on the primary side as described below
A composite resonant converter with a resonant circuit on the secondary side
All basic configurations are adopted. The power supply circuit shown in FIG. 1 is a main power supply switch.
Main switch that operates in response to switch on
Switching converter (main power supply) and main power switch
AC power supply is connected regardless of switch on / off
Standby power supply that operates constantly as long as
Consisting of First, the configuration of the standby power supply unit will be described.
You. For the commercial AC power supply AC, the commercial power transformer S
The primary winding of the BT is connected in parallel. Commercial power transformer
The SBT is provided on the secondary side as described below.
Primary rectifier circuit for generating DC voltage power supply Vcc
Provided to insulate from the side. Commercial power transformer S
For the BT secondary winding, the bridge rectifier circuit Di1 and
And a rectifying / smoothing circuit consisting of a smoothing capacitor Ci1.
Of the commercial AC power supply cycle excited by the secondary winding.
Rectifies and smoothes the current voltage, and supplies a direct current to the smoothing capacitor Ci1.
Is obtained. This rectified smoothed voltage Ei1 is
Input to the three-terminal regulator REG. In the three-terminal regulator REG, the input
The required voltage level is obtained for the rectified smoothed voltage Ei1
The stabilized DC power supply voltage Vcc is output. this
The DC power supply voltage Vcc is output from the three-terminal regulator REG.
Capacitor C1 connected between the power terminal and the secondary side ground
Is obtained as a voltage between both ends. And this DC power supply voltage
Vcc is always used as the operating power supply of the microcomputer 2.
When the microcomputer 2
Regardless of whether the main power switch is on or off,
Operation becomes possible. This microcomputer 2 has C
A PU (Central Processing Unit)
In a given electronic device provided with a power supply circuit,
Execute operation control. The DC power supply voltage Vcc is
-RL is also supplied as a driving power supply. This relay R
L is the main switching as described below.
Provided to control the operation of the converter section on / off
It is. Subsequently, the main power supply section (switching
(Verter section) will be described. ON / OFF of main power supply
The microcomputer 2 drives the relay RL
And the bridge rectifier circuit between the commercial AC power supply AC and the main power supply.
Of the power switch SW inserted between the line and the path Di.
This is done by controlling on / off. Relay R
L is a commercial AC power supply
Line between AC and bridge rectifier circuit Di on the main power supply side
Switch on / off of switch SW inserted between
You. For this relay RL, a microcontroller
Relay drive circuit for driving the relay RL by the computer 2
Roads are connected. This relay drive circuit
It comprises an element Q2, resistors R12, R13 and a diode D.
You. The relay RL has a DC power supply voltage Vcc and a transistor
It is inserted between the collector of Q2 and the transistor Q2.
The transmitter is connected to the secondary side ground. Also Transis
The base of the resistor Q2 is connected to the microcomputer via a resistor R12.
Of on / off signal (ON / OFF) output from data 2
Connected to the power terminal. Also, the resistor R13 is bias set.
For the base of the transistor Q2 and the secondary side ground
Inserted between. Diode D is connected to relay RL
They are connected in parallel according to the direction shown. That is, the relay
Anode at connection point of RL and collector of transistor Q2
And connect the cathode to the DC power supply voltage Vcc
Is what you do. This diode D has, for example, noise and
The reverse current path is formed, and the relay RL malfunctions.
prevent. Here, when the main power supply should be turned off,
In this case, the microcomputer 2 outputs an on / off signal
L level is output as (ON / OFF). in this case
Must have no base current supplied to transistor Q2.
Therefore, the transistor Q2 is off. G
Transistor Q2 is off and collector current does not flow
Relay RL is also in a non-conductive state in the
Main switch SW of AC power supply AC line is off
It becomes. Therefore, the commercial rectifier circuit Di is connected to the bridge rectifier circuit Di.
No power is supplied and the main power supply is turned off. Then, for example, is the main power supply turned off?
When the microcomputer 2 is turned on, the microcomputer 2
Switch the ON / OFF signal (ON / OFF) to H level. this
As a result, the base current flows through the transistor Q2 and
As a result, the transistor Q2 conducts and the collector current flows.
Will be. With this collector current, the relay RL
Is turned on, and the main switch SW is turned on.
You. As a result, the commercial AC power supply AC is
After being supplied to the bridge rectifier circuit Di,
The main power supply unit with the configuration described
You. The bridge rectifier circuit D on the main power supply side
Smoothing capacitor between positive output terminal of i and primary side ground
Ci is connected to the bridge rectifier circuit Di and the smoothing capacitor.
A rectifying / smoothing circuit is formed by the capacitor Ci. this
By the rectifying and smoothing circuit, both ends of the smoothing capacitor Ci are
Is a level corresponding to the same level as the commercial AC power supply AC level.
A rectified smoothed voltage Ei is obtained. This rectified smoothed voltage Ei
DC input voltage for the subsequent switching converter
Supplied as One switching converter on the primary side
Of the switching element Q1. In this figure
Is a switching element Q1 is a symbol as a switch
Although they are equivalently shown by
MOS-FETs, IGBTs, and bipolar transistors
A transistor element such as a star is used. Switchon
The switching element Q1 is connected to a switching transformer TR1 described later.
A series connection circuit is formed by being connected in series with the primary winding N1.
To achieve. And the primary winding N1 side of this series connection circuit is
Connected to DC input voltage line, switching element Q1 side
Is connected to the primary side ground. For the switching element Q1,
For example, a switch that flows when the switching element Q1 is turned on.
Form a current path for flowing the switching current in the reverse direction
Damper diodes are connected in parallel. Further, for the switching element Q1
Is the primary parallel resonance capacitor Cr connected in parallel
You. This primary side parallel resonance capacitor Cr is connected to its own capacitor.
And the primary winding N1 of the switch transformer TR1.
The primary side parallel resonance circuit depends on the leakage inductance.
Form a road. Switching element Q1 performs switching operation
This primary side parallel resonance circuit is
Is performed, the primary side switch including the switching element Q1 is
Switching operation of switching converter is voltage resonance type
And That is, a voltage resonance type converter is provided on the primary side.
Can be The drive circuit 1 includes a switching element Q1
Is driven by the required switching frequency.
Provided for. This drive circuit is switched
When driving the switching element Q1 by separately excited
Is configured using the drive IC. Also, self-excited
In the case of driving more, although not shown here, an example
For example, a drive transformer for driving a switching element,
Connected to the drive terminals (base, gate) of the switching element
A self-excited oscillation driving circuit is provided.
The drive circuit 1 is provided with a photo camera as described later.
Shunt regulator SR input via plastic PC
Input of the constant voltage control signal from
The switching frequency of the switching element Q1 according to the level
By variably controlling the wave number, the secondary side DC output
It also operates to stabilize the pressure Eo. The switching transformer TR1 is connected to the primary side.
With the secondary side insulated, switch the primary side switching output to
Provided for transmission to the next side. This switching
The lance TR1 has, for example, a structure shown in FIG.
That is, two E-shaped cores CR1 and CR2 are prepared. So
The primary winding N is applied to the central magnetic leg of the E-type core CR1.
1 and secondary to the central magnetic leg of E-type core CR2.
The winding N2 is wound. That is, the primary winding N1 and the secondary winding N
2 is divided into different positions and wound. And
E-shaped cores CR1, CR2 thus wound
The magnetic legs of each other so that they face each other
To form an EE-type core. Switching in this way
The transformer TR1 is configured. Here, the switching
In the lance TR1, the primary winding N1 and the secondary winding N2
Because it is divided and wound, primary winding N1 and secondary
Required leakage inductance depending on winding N2
Is obtained. The switching element Q1 is connected to the drive circuit 1.
When the switching operation is performed by driving the
The current as the switching output is the switching transformer TR1
Flows through the primary winding N1, and the primary winding N1
An alternating voltage is generated according to the switching cycle. And
The alternating voltage as the switching output is applied to the secondary winding N
2 will be excited. In this case, with respect to the secondary winding N2, the secondary side
A parallel resonance capacitor C2 is connected in parallel. this
The capacitor of the secondary parallel resonance capacitor C2
The leakage inductance of the secondary winding N2
Therefore, a secondary parallel resonance circuit is formed. To the secondary winding N2
As the alternating voltage is obtained, this secondary side parallel resonance
The circuit will perform a voltage resonance operation. Circuit shown in FIG.
Then, in this way, the switching converter is
Primary side parallel resonance circuit to make the operation of the voltage resonance type
And a secondary side with a secondary parallel resonance circuit.
I am taking it. In other words, the primary side and the secondary side
As a complex resonant converter with a circuit
Have been. As a result, for example, a secondary parallel resonance circuit is provided.
Supply to the load rather than the
Power is increasing. In addition, it shows in FIG.
The circuit has a configuration with a parallel resonance circuit on the secondary side
However, first, the present applicant has proposed a
A configuration having a series resonance circuit on the secondary side has also been proposed. Ma
In addition, a configuration having a partial voltage resonance circuit has been proposed. Book
As an embodiment, such a composite resonance type converter
It does not matter. In this case, the secondary winding N2 is not shown.
The rectifier diode Do and the smoothing capacitor Co
Is formed. And this
Due to the operation of the half-wave rectifier circuit, both the smoothing capacitor Co
The secondary DC output voltage Eo is obtained as the terminal voltage. this
The secondary side DC output voltage Eo is controlled by a load as a load (not shown).
Supplied to the road. Subsequently, the configuration of the constant voltage control circuit system
explain. In this figure, the constant voltage control circuit
Output resistors R1, R2, shunt regulator SR, and
It is formed with a photocoupler PC. Voltage detection resistors R1,
R2 is connected in series as shown in FIG.
It is inserted between the flow output voltage Eo and the secondary side ground.
Then, the connection point between the voltage detection resistors R1 and R2 and the shunt resistor
And the detection input terminal of the comparator. Chantregi
The anode of the condenser SR is connected to the secondary side ground.
The cathode is the photodiode of the photocoupler PC
Connected to the anode side of Photodiode, DC
To obtain the operating power from the voltage power supply Vcc, the cathode side
Is connected to a DC voltage power supply Vcc via a resistor R10.
You. Depending on the series connection of the resistors R1 and R2, the secondary
Side DC output voltage Eo is divided, and the divided
Current output voltage Eo to the shunt regulator SR detection input
Enter for. In the shunt regulator SR,
The divided voltage level of the secondary side DC output voltage Eo
Compare with reference voltage level. Shunt regulator SR
, The divided voltage of the input secondary side DC output voltage Eo
Level according to the error between the level and the internal reference voltage level.
It operates to draw current into the cathode. This
Input to the photodiode of the photocoupler PC.
Level according to the error between the divided voltage level and the internal reference voltage
Current flows. The photo coupler PC
Collector current according to the current level flowing through the
To the photo transistor on the side. This file
The collector current flowing through the transistor
Is supplied as a constant voltage control signal. like this
In addition, the photocoupler PC detects the level of the secondary side DC output voltage Eo.
The constant voltage control signal according to the bell error is sent to the primary and secondary
Are transmitted in a DC-insulated state. In the drive circuit 1, the input constant voltage system
Switching of switching element Q1 based on control signal
The frequency is variably controlled. In this case, heavy load and low
The output voltage tends to decrease and the secondary DC output voltage Eo decreases.
Switching frequency, lower the switching frequency.
The driving of the switching element Q1 is controlled so that Reverse
In addition, light load and high input voltage become the secondary DC output voltage
When Eo increases, increase the switching frequency.
Drive control. Note that the constant voltage control signal is actually
Of the shunt regulator SR flowing through the coupler PC
It becomes a draw current. Therefore, the constant voltage control signal
The current level changes to the secondary side DC output
The pressure increases as the pressure Eo increases, resulting in a heavy load
It decreases as the secondary side DC output voltage Eo decreases.
You. In the drive circuit 1, the constant voltage control signal is used.
When the current increases, the switching element Q1 is turned off.
It works to shorten the interval (TOFF),
Control is performed to increase the switching frequency. Conversely, constant voltage
If the current as the control signal decreases, the switching element
This operates to extend the off period (TOFF) of the child Q1.
Control to lower the switching frequency.
You. Thus, the primary side switching element Q
By variably controlling the switching frequency of 1
Is the resonance impedance of the complex resonant converter
Will change. And this is the primary side
The switching output transmitted to the secondary side changes from the secondary
The level of the side DC output voltage Eo is changed. As a result,
The secondary side DC output voltage Eo is stabilized. Note that the voltage
In the case of an oscillatory converter, within one switching cycle
During the off period, the primary side parallel resonance capacitor Cr and the secondary side
Of the primary winding N1 and secondary winding N2
Certain time determined by cage inductance
You. Therefore, the variable control of the switching frequency requires only one switch.
Performed by changing the ON period in the switching cycle
Will be. By the way, the configuration shown in FIG.
Frequency characteristics of resonance circuit system in combined resonance type converter
Is as shown in FIG. In other words, depending on the resonance frequency
Gain at a specific frequency
Will be. And change the switching frequency
Range of the switching frequency for constant voltage
The box is shown as "operating frequency range" in the figure.
For example, the frequency between two frequencies where the gain is peaked
Use the wave number range. The switching of the power supply circuit shown in FIG.
The voltage Vce across the element Q1 and the switching current Ic
The operation is similar to the waveform shown in FIG.
That is, the switching element Q1 shown in FIGS.
Is zero level during the ON period TON.
In the off period TOFF, the bell
Thus, a waveform is obtained in which a voltage resonance pulse can be obtained. Also,
It flows through the switching element Q1 shown in FIGS.
The switching current Ic changes from the negative polarity during the period TON.
Flows as a sawtooth wave that turns to positive polarity and smells during TOFF
To the 0 level. Then, the switching cycle (TON + TOF)
FIG. 6 (F) shows a lower light load than that of FIGS. 6 (c) and 6 (d).
(A) The light load shown in (b) is longer
I understand. That is, as described above, from light load to heavy load
The switching frequency decreases as the load tends to
Be controlled so that. The period TOFF is constant,
Switching frequency can be set by changing TON between
Weird. This is, for example, in the characteristic diagram of FIG.
The relationship between the load current (load power) and the peak voltage Vce-peak is also
This is the same as the contents described above with reference to FIGS. One
In other words, the load current increases due to the tendency of heavy load.
, The peak voltage Vce-peak increases. Also, enter
The peak voltage is higher when the input voltage is higher than when it is lower.
Vce-peak increases. The power supply circuit of the present embodiment shown in FIG.
In the above, the soft start
Roads are provided. Hereinafter, the configuration of this soft start circuit
And its operation will be described. The soft start circuit of the present embodiment has the following
It is formed in such a manner. In this case, first switch
A tertiary winding N3 is wound around the transformer TR1. This
One end of the tertiary winding N3 is connected to the secondary side ground,
Is connected to the secondary side ground through the series connection of the voltage dividing resistors R7 and R8.
Connect to The connection point between the voltage dividing resistors R7 and R8 is
Connected to the base of transistor Q6. Transistor Q6
When the collector is connected to the base of transistor Q5
Both are connected to the emitter of the transistor Q5 via the resistor R6.
Continued. The emitter of transistor Q6 is grounded on the secondary side
Connected to The emitter of the transistor Q5 is
On / off signal (ON / OFF) output from computer 2
And the collector is connected through a voltage dividing resistor R4-R5.
Connected to secondary ground. The above voltage divider resistor
The connection point of R4-R5 is connected to the base of transistor Q4.
Connected. The collector of the transistor Q4 has a time constant
Connected to the base of transistor Q3 via capacitor C3.
Of the transistor Q3 via the resistor R3.
Connected to the The emitter of transistor Q3 is
Photocoupler of photocoupler PC (Anode → Casor)
-) Connected to DC voltage power supply Vcc via resistor R10
Continued. The collector of the transistor Q3 is the secondary side ground.
Connected to Then, the book formed as described above is used.
The operation of the soft start circuit according to the embodiment is as follows.
You. Here, to activate the power supply circuit,
Computer 2 outputs an L level signal as an on / off signal (ON / OFF).
Level (0 level) is output,
It is assumed that the output has been switched. As a result, the relay RL
Driven to conduct, main switch SW is off
The state is switched to the ON state. Main switch
When the switch SW is turned on, the rectifier circuit on the main power supply side
(Di, Ci) is supplied with a commercial AC power supply AC,
A rectified smoothed voltage Ei is generated across the capacitor Ci. On the other hand, the microcomputer 2 outputs an H level signal.
When the on / off signal (ON / OFF) of the
Start supplying voltage to the collector of transistor Q5
It will also be. However, the transistor Q5
The base is connected to the collector of transistor Q6.
Therefore, the on / off state of the transistor Q5
This is linked with the on / off state of the register Q6. G
The base of transistor Q6 is the connection point of voltage dividing resistors R7-R8
But the voltage dividing resistors R7-R8 are connected to the tertiary winding N3.
Is connected to The tertiary winding N3 is a switching transformer.
The main switch is
The alternating voltage is excited by performing the switching operation.
You. Therefore, the transistor Q6 is connected to the switching element Q1.
Is in a switching operation and the switch is
Only in response to the timing when the switching element Q1 turns on
It turns on. Thus, the tertiary winding N3 and the transformer
Circuit Q6 and a voltage divider R7-R8.
Means that the switching element Q1 is ON
It has the function to do. And the transistor Q6
Lector is connected to the base of transistor Q5
The transistor Q5 also turns on the switching element Q1.
So that it is turned on only at certain times.
It is. When the transistor Q5 is turned on and the emitter
-Depending on the current flowing between the collectors,
The collector current of transistor Q5 is connected to voltage dividing resistors R4-R5
Flows through the point to the base of transistor Q4,
The star Q4 is also turned on. Transistor Q4
Is on, charge current to the time constant capacitor C3
So that the base current of the transistor Q3 flows.
The transistor Q3 is also turned on and the emitter-collector
Current flows through the The emitter of transistor Q3 is
The photodiode of the photocoupler PC is connected
If the transistor Q3 is on, this transistor
Current will flow through the photodiode. As can be seen from the above description, the
When the transistor Q3 turns on, the primary side switching
Only when the element Q1 is in the ON state. Therefore,
Pass current to photodiode by transistor Q3
The timing also indicates that the switching element Q1 is in the ON state.
Only. Here, when the power is turned on, the secondary side
Since the DC output voltage Eo is not generated, the normal constant voltage
The shunt regulator SR that forms the control circuit system
Therefore, no current flows through the photodiode. Follow
When the power is turned on, the soft start circuit
Switching element Q1 performs switching and turns on.
Only via the photocoupler PC
As a result, a constant voltage control signal flows through the drive circuit 1.
You. The output from the soft start circuit is
The initial constant voltage control signal is, for example, a switching element
So that Q1 has a higher switching frequency than required
It is set to be a level for performing By the way, the switching frequency is increased.
That the drive circuit 1 controls the
To shorten the on-period of the switching element Q1.
And act to turn off the switching element Q1.
It can be said that there is. However, as mentioned above
Only during the period when the switching element Q1 is turned on.
If the constant voltage control signal flows accordingly,
Sometimes, the switching element Q1 is driven
A state in which a current as a constant voltage control signal is not supplied to the circuit 1
State from the off state to the on state.
You. That is, when the switching element Q1 is turned on,
Drive circuit 1 turns off switching element Q1.
The switching element is not working.
The child Q1 can be stably turned on. Toes
As a result, a stable starting operation can be obtained. Then, as described above, the switching element
When the child Q1 transitions from the off state to the on state,
The operation of the soft start circuit allows the photocoupler PC
Current through the photodiode
The constant voltage control signal is supplied to the circuit 1. This
As a result, the drive circuit 1 switches the switching element Q1
Controlled to be in the off state and switched on
The switching element Q1 is turned off. Switching
When the element Q1 is turned off, the soft start circuit
Transistor Q3 is also turned off, and constant voltage control is performed.
The supply of the signal will be stopped. Therefore, the switch
When the switching element Q1 turns on from this off state,
Means that the drive circuit 1 turns off the switching element Q1.
Control is not being performed.
The switching element Q1 can be turned on stably
Become. FIG. 4 shows the timing chart of FIG.
Operation at power-on for the power supply circuit
Have been. As shown in FIG.
The on / off signal output from computer 2 is off (L
By switching from the bell to the H level, the main switch
Switch is turned on and the commercial power supply
It is assumed that AC is input. Switching elements are
Rectified and smoothed voltage Ei generated by turning on the power supply AC
To start switching operation. Then, if
As shown in FIGS. 4B and 4C, the switch
According to the timing at which the switching element Q1 is turned on,
Make the current (constant voltage control signal) flow to the top coupler PC
Is done. Thereby, as described above, the switching element
Q1 is turned on stably. Toes
The switching element Q1 becomes stable when the power is turned on.
To start the switching operation. The base of the transistor Q3 and the transistor
A time constant capacitor C3 is connected between the collector of the
Is inserted, and as shown in FIG.
When a current flows through the coupler PC, this time constant capacitor
The base current of the transistor Q3 flows into the capacitor C3 and is charged.
Will be. Then, the switching element Q1 is turned on.
By repeating / off, the time constant capacitor C
Since the amount of charging current in 3 will increase,
The base potential of the transistor Q3 gradually decreases
Will be. Therefore, the current flowing through the photocoupler PC
(Equivalent to the collector current of transistor Q3)
As shown in FIG. 4 (c), as shown in FIG.
It will decrease. This is seen from the drive circuit 1.
If this happens, the level of the constant voltage control signal will decrease.
Therefore, as the drive circuit 1, the switching frequency
Is controlled to be lower. This is the figure
The ON period of the switching element Q1 in FIG.
Indicated by being too long.
That is, when the power is turned on, the switching element Q1
Initially turns on / off at a high switching frequency,
It is controlled so that the switching frequency decreases
Will be. In this embodiment, the switching operation is cheap.
Since the power supply is started regularly, the switch
Of the switching element Q1
Can be faster. Immediately after the power is turned on, the constant voltage control signal
The signal level is high and the switching frequency is high
It is in a state where it is controlled as follows. And at this time Sui
The switching element Q1 starts switching operation.
Therefore, as shown in FIG. 4D and FIG.
In the switching element at the beginning of
The current Ic can be very small. Also this
, The voltage Vce across the switching element Q1 (resonance
The peak level of the pulse is also sufficiently suppressed. It should be noted that depending on the lapse of time after the power is turned on,
The levels of the switching current Ic and the resonance pulse gradually increase
Although it will increase, it will be sufficiently suppressed at the beginning.
The voltage across the switching element Q1
Make sure that the peak level of Vce does not exceed the rating.
It is. Thus, in the present embodiment, the switching
Strong protection without giving stress to element Q1
Then, the main power supply unit can be started. In addition,
The voltage level across switching element Q1
The switching element Q1
It is possible to select a product with a lower breakdown voltage than before.
As a result, for example, cost reduction and miniaturization are achieved.
Also, it is possible to obtain better switching characteristics.
You. Then, as described above, the switching element
Child Q1 repeats on / off and the time elapses
In some cases, the switching element Q1 is turned on and
Each time the voltage control signal flows, the time constant capacitor C3
The battery is charged. And every time charging is done
As the charging potential increases, the transistor Q
The base potential of 3 decreases. And a certain timing
The base potential of the transistor Q3 becomes lower than a certain level.
Then, the transistor Q3 is turned off. In other words, softs
The start operation will be stopped. Soft start operation
When the operation stops, the secondary side DC output voltage Eo rises
Has almost reached the specified level,
Constant voltage by constant voltage control circuit system with regulator SR
The voltage control signal is fed back to the drive circuit 1 and the normal constant voltage
The operation will shift to the control operation. It should be noted that the present invention is not limited to the above-described embodiment.
The configuration is not limited to the actual specification, etc.
It can be changed appropriately as needed. For example, in the above embodiment,
The compound resonance type converter is a primary side voltage resonance type switch.
As a switching converter with a single switching element
It adopts a single-end configuration.
Push-pull configuration with switching elements
It can also be applied when taking. In addition, the primary side switching
Also applicable to complex resonance type converters with current resonance type inverters
It is possible to do. As described above, the present invention provides a switch
Resonance type capacitor with constant voltage control by switching frequency control
After the basic configuration as a barter,
To protect the switching element from excessive current and voltage
A soft start circuit is provided. Softs according to the invention
The start circuit is activated for a certain period after the power is turned on.
In order to maintain the above switching frequency,
Current flowing through the switching element and
Suppress voltage. And the switching frequency
When controlling more than necessary, the switching element
Set the switching frequency only when it is on.
Output a constant voltage control signal to control more than necessary
Is configured. This allows the switching element to be turned off.
At the point when the switching frequency
The constant voltage control signal to control the number
The switching element is stable
It is possible to make a transition from the on state to the off state. As a result, although the soft start circuit is provided,
Also, the switching element is stable after the power is turned on.
, The switching operation can be started. Ma
In addition, stable startup is possible, so that
Since the start is started at the same time, the current and
Voltage and voltage are sufficiently suppressed to protect the switching element
The function will also be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a configuration example of a switching power supply circuit according to an embodiment of the present invention. FIG. 2 is a perspective view showing a structural example of a switching transformer provided in the switching power supply circuit of the present embodiment. FIG. 3 is a diagram illustrating a relationship between a resonance frequency and an operating frequency range of the switching power supply circuit according to the present embodiment. FIG. 4 is a timing chart illustrating an operation of the switching power supply circuit according to the present embodiment when the power supply is started. FIG. 5 is a circuit diagram showing a configuration example of a switching power supply circuit as a conventional example. FIG. 6 is a waveform chart showing switching operations of the power supply circuit shown in FIG. 5 under light load and heavy load. FIG. 7 shows a load current and a load current of the power supply circuit shown in FIG.
FIG. 4 is a characteristic diagram showing a relationship between a parallel resonance pulse applied to a switching element and a peak level. 8 is a timing chart showing an operation of the power supply circuit shown in FIG. 5 at the time of starting up the power supply. 9 is a circuit diagram illustrating a configuration example of a switching power supply circuit configured by adding a soft start circuit to the power supply circuit illustrated in FIG. 5; FIG. 10 is a timing chart showing an operation of the power supply circuit shown in FIG. 9 when the power is turned on. [Description of Signs] 1 Drive circuit, 2 microcomputer, SW
Main switch, Di bridge rectifier circuit, Ci smoothing capacitor, Q1 switching element, Cr primary side parallel resonance capacitor, TR1 switching transformer, N1
Primary winding, N2 secondary winding, C2 secondary side parallel resonant capacitor, SR shunt regulator, Q3, Q4, Q5,
Q6 transistor, C3 time constant capacitor

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5H730 AA20 AS01 BB23 BB57 BB72                       BB80 BB95 CC01 DD03 DD04                       DD26 EE02 EE07 EE59 FD01                       FG01 FG25 VV01 XC04 XC14

Claims (1)

1. A rectifying / smoothing means for generating a DC input voltage by inputting a commercial AC power and performing a rectifying / smoothing operation, and a switching element for intermittently outputting the DC input voltage. Switching means formed by switching, a drive circuit for switchingly driving a switching element forming the switching means, an insulating switching transformer for transmitting a switching output of the switching means from a primary side to a secondary winding, at least: A primary-side resonance circuit formed by a leakage inductance of a primary winding of the switching transformer and a capacitance of a primary-side resonance capacitor, the primary-side resonance circuit being provided to make the operation of the switching means a resonance type; The leakage inductance of the wire and this secondary winding A secondary-side resonance circuit formed by the capacitance of a secondary-side resonance capacitor connected to the line; and an alternating current formed by including the secondary-side resonance circuit and obtained in a secondary winding of the switching transformer. Enter the voltage,
Voltage generating means configured to output a secondary-side DC output voltage, and a constant-voltage control signal corresponding to the level of the secondary-side DC output voltage is output to the drive circuit, so that the switching element Constant voltage control means for variably controlling the switching frequency of the switching element; detecting a period during which the switching element is turned on during a certain period after the power is turned on; and only during this detected period, the switching frequency of the switching element is higher than required. And a soft-start circuit configured to output a constant voltage control signal to be maintained in the drive circuit to the drive circuit.