JP2653713B2 - Switching regulator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input / output insulated switching regulator, and more particularly to a switching regulator with a simplified circuit configuration.

[Prior Art] As a conventional switching regulator, there is one having a circuit shown in FIG. That is, the rectified voltage V _IN obtained by rectifying the AC voltage from the AC power supply 2 with the rectifier 4 and smoothing the AC voltage with the smoothing capacitor 6 is supplied to the first power converter 8 and the second voltage converter 10. Through this, a stable DC voltage Vo is generated.

That is, the first power converter 8 converts the intermittent energy sent from the input _VIN by the switching operation of the switching transistor Q1 into the choke coil CH and the capacitor.
LC filter consisting of C1 and flywheel diode D1
The pulse width control circuit 12 detects the voltage fluctuation of the DC stabilization voltage Vc and averages the DC fluctuation voltage of the switching transistor Q1 so as to suppress the voltage fluctuation. Performs control (PWM).

The second power converter 10 converts the stabilized DC voltage Vc into a high-frequency pulse signal again by the switching operation of the transistor Q2 connected in series to the primary winding L1 of the high-frequency transformer T, Generated in the rectifier diode
By rectifying and smoothing with D2 and the smoothing capacitor Co, a stabilized DC voltage Vo is generated. Further, the pulse width control circuit 14 detects the voltage fluctuation of the voltage Vo due to the fluctuation of the load RL, and controls the conduction period of the switching transistor Q2 so as to suppress the voltage fluctuation.

Thus, the first power conversion unit 8 and the second power conversion unit
According to the switching regulator in which 10 is connected in series, the voltage Vc can be stabilized by the operation of the first power conversion unit 8 even if the voltage amplitude of the AC power supply 2 fluctuates greatly. Has the advantage that it can be done with a minimum value.

For example, in a case where the first power conversion unit 8 is omitted and a circuit configuration in which the voltage Vin of the smoothing capacitor 6 is directly supplied to the capacitor C1, a capacitor having a withstand voltage equal to or larger than the maximum voltage amplitude of the AC power supply 2 is required. Furthermore, in order to supply sufficient power to the load even at the time of the minimum amplitude, it is necessary to provide an extremely large-capacity capacitor.

On the other hand, by providing the first power conversion circuit 8,
It is possible to generate a stabilized DC voltage with a low withstand voltage and a small capacity capacitor.

[Problems to be Solved by the Invention] However, such a conventional switching regulator has a problem that the circuit scale becomes large because the switching transistor and the pulse width control circuit are provided in each power conversion circuit. Was.

The present invention has been made in view of such a problem, and has as its object to provide a switching regulator having a small circuit scale.

[Means for Solving the Problems] For such a purpose, the present invention provides a rectifying circuit for rectifying an AC voltage, and a chopping of a rectifying current generated in the rectifying circuit by controlling an energizing period of a switching element. Is generated, and the crossing current is smoothed by a filter including a choke coil and a capacitor, so that the first DC current is generated.
A first power conversion unit for generating a voltage, and a capacitor first voltage of the first power conversion unit being chopped by energizing period control of a switching element to supply an intersecting current to a primary winding of a transformer. And a switching regulator that generates a second DC voltage by smoothing the voltage induced in the secondary winding with a filter.

The switching element of the first power conversion unit is shared by the switching element of the second power conversion unit, and at least the first element generated in the first power conversion unit.
A configuration is provided that includes a pulse width control unit that controls a conduction period of the switching element in response to a change in the voltage and the second voltage generated in the second power conversion unit.

[Operation] In the switching regulator of the present invention having such a configuration, the chopping operation of the first power converter and the second power converter is shared by one switching element, and the switching element Is controlled by a common pulse width control circuit, so that the circuit can be miniaturized without deteriorating the voltage stabilizing function of the first power conversion unit and the second power conversion unit. it can.

Further, the present invention can be applied to both a separately-excited switching regulator and a self-excited switching regulator.

Example A first example of the present invention will be described with reference to the drawings. First, the circuit configuration will be described with reference to FIG. 1. This rectifies a rectified voltage V _IN obtained by rectifying an AC voltage supplied from an AC power supply 2 with a rectifier 4 and smoothing with a smoothing capacitor 6 to a first power. This is a separately-excited switching regulator that generates a stable DC voltage Vo by passing it through the converter 8 and the second power converter 10.

That is, the diodes D11 and D12 are connected to the choke coil CH connected to one end of the smoothing capacitor 6, the primary winding L1 of the high-frequency transformer T is connected between the cathodes of these diodes D11 and D12, and the cathode contact of the diode D11 is connected. And a capacitor C1 is connected between the other end of the capacitor 6 and
The switching transistor Qs is connected between the cathode contact of the diode D12 and the other end of the capacitor 6.

A rectifier diode D2 and a smoothing capacitor Co are connected in series between both ends of the secondary winding L2 of the high-frequency transformer T,
Apply the stabilized voltage Vo generated across the smoothing capacitor Co to the load RL.
To be supplied.

Further, the switching transistor Qs is controlled by a pulse width control circuit. That is, the pulse width control circuit sequentially compares the voltage Vo across the capacitor Co with the reference voltage V _REF , the voltage Vc across the capacitor C1 and the reference voltage V _REF
, A oscillating circuit 20 that outputs a triangular wave signal Sa having a frequency corresponding to the voltage of the difference signal Δ1 output from the differential amplifying circuit 16, and a triangular wave signal from the oscillating circuit 22.
The differential amplifier 22 generates a short-wave drive signal Sb by comparing the voltage of Sa with the voltage of the difference signal Δ2 from the differential amplifier circuit 18.

Here, the inductance of the choke coil CH is set so that a current equal to or more than the critical current flows in order to satisfy the condition that the switching transistor Qs repeats the on / off operation to be in the continuous mode at the full load when the switching transistor Qs repeats the on / off operation. The inductance of the secondary winding L2 of T is set so that a current equal to or less than the critical current flows in the intermittent mode.

The turns ratio between the primary winding L1 and the secondary winding L2 of the high-frequency transformer T is set to an appropriate ratio n ₁ : n ₂ .

 Next, the differential of the first embodiment will be described.

First, by repeating the on-off operation switching transistor Qs is in synchronization with the driving signal Sb, the source-drain voltage V _CE of the switching transistor Qs is changed as shown in FIG. 2 (a). Accordingly, the second
As shown in FIG. 7B, during the period T _ON when the switching transistor Qs is turned on, the voltage V across the choke coil CH.
_{1 is} substantially equal to the voltage V _{IN of the} capacitor 6, and during the period T _OFF when the switching transistor Qs is turned _off , the voltage v ₁ across the choke coil CH is changed from the voltage V _IN to the capacitor C1.
Becomes substantially equal to the voltage V _IN −Vc obtained by subtracting the voltage Vc between both ends. Then, the choke coil CH average current i ₁ flows as shown in FIG. 2 (c).

Further, when the voltage V _IN rises due to the voltage fluctuation of the AC power supply 2 and the voltage Vc across the capacitor C1 rises accordingly, the differential amplifier 18 detects the difference corresponding to the difference between the reference voltage V _REF and the voltage Vc. The signal Δ2 is output, and the differential amplifier 22 compares the triangular wave signal Sa from the oscillation circuit 20 with the difference signal Δ2, thereby shortening the period during which the drive signal Sb is at the “H” level. As a result, the conduction period T _ON of the switching transistor Qs is shortened, and the feedback control for suppressing the rise of the voltage Vc of the capacitor C1 is automatically performed.

Conversely, voltage V _IN drops due to the voltage fluctuation of AC power supply 2,
When the voltage Vc across the capacitor C1 drops accordingly, the period during which the drive signal Sb is at the "H" level becomes longer by the same feedback control, so that the conduction period T _ON of the switching transistor Qs becomes longer, Suppress the drop of the voltage Vc of the capacitor C1.

Thus, the conduction period of the switching transistor Qs
By automatically controlling the T _ON, it is possible to always keep the voltage Vc of the capacitor C1 constant.

Further, the thus stabilized voltage Vc, by chopping the on-off operation of the switching transistor Qs, so that the voltage across v ₂ of the primary winding L1 of the high-frequency transformer T is shown in FIG. 2 (d) And the primary winding L1
₂ changes as shown in FIG. 2 (e).

Then, a current i ₃ as shown in FIG. 2 (f) flows through the secondary winding L2, and this current i _{3 is connected} to a diode D2 and a capacitor.
DC voltage Vo is generated by rectifying and smoothing with Co.

Further, with the variation of the current flowing through the load RL, when the voltage Vo drops, by the differential amplifier 16 is compared with the reference voltage V _REF, the output of the difference signal Δ1 corresponding to the drop of the voltage Vo I do. Then, the oscillation circuit 20 generates a triangular wave signal Sa having a lower frequency by the voltage of the difference signal 1, and the driving signal Sb having a longer "H" level period from the differential amplifier 22 to the switching transistor Qs by the lower frequency. Supply. As a result, the current i flowing through the primary winding L1 of the high-frequency transformer T
₂ increases as shown by the dotted line in FIG. 2 (e), and accordingly, the current i ₃ induced in the secondary winding L2
Also acts to suppress the drop of the voltage Vo of the capacitor Co.

Conversely with the variation of the current flowing through the load RL, when the voltage Vo rises, by the differential amplifier 16 is compared with the reference voltage V _REF, the output of the difference signal Δ1 corresponding to the increase in the voltage Vo Then, the oscillation circuit 20 generates a triangular wave signal Sa having a higher frequency by the voltage of the difference signal Δ1, and the driving signal Sb having a shorter “H” level period from the differential amplifier 22 to the switching transistor Qs by the higher frequency. Supply. As a result, the current i ₂ flowing through the primary winding L1 of the high-frequency transformer T is reduced,
Along with this, in a reducing current also i ₃ induced in the secondary winding L2, acts to suppress the increase of the voltage Vo of the capacitor Co.

Thus, the conduction period of the switching transistor Qs
By automatically controlling T _ON , the voltage Vo of the capacitor Co can always be kept constant even if the voltage of the load RL fluctuates.

Conventionally, feedback control for stabilizing the output voltage of each of the first power exchange unit and the second power exchange unit is performed by a separate switching transistor and pulse width control circuit. In this example,
Since the switching transistor and the pulse width control circuit are shared by the respective power conversion units, the circuit scale can be reduced.

Next, a second embodiment will be described with reference to FIG. this is,
This is a modification of the pulse width control circuit of the embodiment shown in FIG. That is, the voltage Vo of the capacitor Co and the reference voltage V _REF
Is compared with the differential amplifier 16 to generate a difference signal Δ1 corresponding to the variation, and the voltage Vc of the capacitor C1 and the reference voltage V _REF are compared by the differential amplifier 18 to correspond to the variation. Generating a difference signal Δ2,
The voltage obtained by multiplying the difference signal Δ2 by the voltage V _IN generated in the capacitor 6 by the multiplier 24 is supplied to the oscillation circuit 20. Then, the oscillation circuit 20 generates a triangular wave signal Sa whose oscillation frequency is changed by an amount corresponding to the multiplication result, and the differential amplifier 22 compares the triangular wave signal Sa with the difference signal Δ1, so that the energizing period of the switching transistor Qs Generates a drive signal Sb for controlling

According to the second embodiment, since the energization period control of the switching transistor Qs is performed including the fluctuation of the voltage V _IN generated by the capacitor C1, the output voltage Vc of the first power conversion unit is controlled.
Can be further stabilized and the power factor can be improved.

In the second embodiment, the energization period of the switching transistor Qo is controlled by changing the frequency of the drive signal Sa in response to the change in the first voltage.
In the first embodiment, the drive signal Sa corresponds to the variation of the second voltage.
The following configuration is employed to control the energization period of the switching transistor Qo by changing the frequency of the switching transistor Qo. However, both can stabilize the first voltage and the second voltage.

The above controls the energization period, that is, controls the position, length, cycle, etc. of the intermittent pulse, and as a result, the so-called PW
It controls the presence / absence of signals on various time axes such as M, PFM, PPM, PCM, etc., and determines ON / OFF of a pulse according to one signal change and performs one control.

Among those performing such control, the conduction period can be controlled by turning off the switching element in the on state at a required timing after a certain period, that is, controlling the off timing.

Also, by turning on the switching element in the off state at a necessary timing after a certain period,
That is, the non-conductive period can be controlled by controlling the ON timing.

Therefore, by dividing the two independent signal changes into control of the conduction period and control of the non-conduction period, one of the characteristics of the controlled side responds to the PWM signal.
If it is configured not to respond to the FM signal and the other is configured not to respond to the PFM signal but to the PWM signal, it is possible to control each independently.

4 and 5 described below are provided with a dedicated circuit used only for turning on the switching element Qs and a dedicated circuit used only for turning off the switching element Qs, each of which is provided with a smoothing capacitor VC and an output voltage. It is driven independently by VO, and there is a difference in the inductance value that acts as a filter. One is below the critical current (the inductance is small and responds to the PFM signal), and the other is above the critical current (the inductance is large and the PWM signal is large). Responds to)
By doing so, it is possible to control both voltages with one element.

 Next, a third embodiment will be described with reference to FIG.

This is a self-excited switching regulator.
That is, by controlling the non-conductive period of the switching transistor Qs in synchronization with a current change induced in the winding L3 wound on the primary winding L1 side of the high-frequency transformer T, the capacitor of the first power conversion unit is controlled. The voltage Vc generated in C1 is stabilized. Further, a voltage obtained by dividing the output voltage Vo by the resistors R1 and R2 is detected by the voltage detection circuit 26, and a current corresponding to the variation of the output voltage Vo is supplied to the photodiode PD. Photo transistor PT
By automatically adjusting the bias point of the switching transistor Qs according to the fluctuation of the output voltage Vo,
The conduction period of the switching transistor Qs is controlled so as to suppress the fluctuation of the output voltage Vo.

According to this embodiment, the power factor of the AC input can be improved, and the first and second power converters are controlled by the common switching transistor and the pulse width control circuit. Can be.

Next, a fourth embodiment will be described with reference to FIG. This is a self-excited switching regulator, and the capacitor 6
Both ends of the primary winding L3 of the transformer T2, the switching transistor Qs, and the choke coil CH1 are connected in series, and both ends of the primary winding L1 of the high-frequency transformer T, the primary winding L3 of the transformer T2, the switching transistor Qs, It has a circuit in which the capacitor C1 and the diode D3 are connected in series. Then, by automatically adjusting the bias point of the switching transistor Qs in accordance with the change in the current induced in the secondary winding L4 of the transformer T2 and performing the non-conductive period control, the capacitor C1 of the first power conversion unit is controlled. Generated voltage Vc
Stabilize. Further, a voltage obtained by dividing the output voltage Vo by the resistors R1 and R2 is detected by the voltage detection circuit 26, and a current corresponding to the variation of the output voltage Vo is supplied to the photodiode PD. The light emission is received by the phototransistor PT, so that the bias point of the switching transistor Qs is automatically adjusted according to the variation of the output voltage Vo, and the conduction period of the switching transistor Qs is controlled to suppress the variation of the output voltage Vo. It has become.

Next, a fifth embodiment will be described with reference to FIG. This is a separately-excited and forward-type switching regulator. That is, the first power converter includes the choke coil CH for generating a stable voltage Vc across the capacitor C1, the capacitor C1, and the freewheel diode 3, and
The power converter includes a forward-type circuit including diodes D21 and D22 and a choke coil CH2 subsequent to the secondary winding L2 of the high-frequency transformer T.

Then, by comparing the voltage Vo of the capacitor Co with the reference voltage _VREF by the differential amplifier 16, a difference signal Δ1 corresponding to the variation is generated, and the voltage Vc of the capacitor C1 is compared with the reference voltage _VREF. , A difference signal Δ2 corresponding to the variation is generated. Further, the oscillation circuit 20 generates a triangular signal Sa whose oscillation frequency is changed by an amount corresponding to the difference signal Δ2, and the differential amplifier 22 generates a triangular wave. By comparing the signal Sa and the difference signal Δ1, the switching transistor
A drive signal Sb for controlling the conduction period of Qs is generated.
As described above, according to this embodiment, since the forward method is applied, the output voltage Vo with little ripple can be generated.

[Effects of the Invention] As described above, according to the present invention, the operation control of the first and second power converters is performed commonly by one switching transistor and the pulse width control circuit. Therefore, the number of components for configuring the device can be reduced, and the device can be reduced in size, cost, weight, and the like can be realized. Further, the distortion of the AC input current can be reduced and the power factor can be improved by adding only a small number of components.

[Brief description of the drawings]

 1 is a circuit diagram of a first embodiment of the present invention; FIG. 2 is a waveform diagram for explaining the operation of the first embodiment; FIG. 3 is a circuit diagram of a second embodiment of the present invention; 5 is a circuit diagram of a third embodiment of the present invention; FIG. 5 is a circuit diagram of a fourth embodiment of the present invention; FIG. 6 is a circuit diagram of a fifth embodiment of the present invention; FIG. Symbols in the figure: 2; AC power supply 4; Rectifier 6; Capacitor 8; First power converter 10; Second power converter 16, 18, 20; Differential amplifier 20; Oscillator 24; Multiplier 26; : Voltage detection circuit Qs; Switching transistor CH, CH1, CH2; Choke coil T; High-frequency transformer T1; Transformer L1 to L4; Winding D1, D2, D3, D11, D12, D21, D22; Diode C1, Co; Capacitor R1 , R2; resistor PD; light emitting diode PT; phototransistor RL; load

Claims (5)

(57) [Claims] A rectifier circuit for rectifying an AC voltage, a chopping current generated by chopping a rectifying current generated in the rectifying circuit by controlling an energizing period of a switching element, and further generating a chopping coil and a capacitor. A first power exchange unit that generates a first DC voltage by smoothing with a filter consisting of: a chopping of a capacitor output of the first power exchange unit by controlling a conduction period of a switching element to reduce an intersecting current; A switching regulator having a second power converter that supplies a primary winding of a transformer and generates a second DC voltage by smoothing a voltage induced in a secondary winding of the transformer by a filter circuit. The switching element of the first power converter is shared by the switching element of the second current converter, and the first and second power converters The inductance of each power conversion unit is set so that one of the currents flowing through the first power conversion unit is equal to or more than the critical current value and the other current is equal to or less than the critical current value, and the first voltage generated in the first power conversion unit By controlling the conduction period of the switching element in accordance with the fluctuation of the first voltage, the fluctuation of the first voltage is suppressed, and the non-conduction period of the switching element in response to the fluctuation of the second voltage generated in the second power converter. And a pulse width control means for controlling the fluctuation of the second voltage by controlling the switching regulator. 2. A rectifying circuit for rectifying an AC voltage, and a rectifying current generated in the rectifying circuit is chopped by controlling a conduction period of a switching element to generate a crossing current, and the crossing current is further converted to a choke coil and a capacitor. A first power conversion unit that generates a first DC voltage by smoothing with a filter consisting of: and a capacitor output of the first power conversion unit is chopped by controlling a conduction period of a switching element to reduce an intersecting current. A switching regulator having a second power converter that supplies a primary winding of a transformer and generates a second DC voltage by smoothing a voltage induced in a secondary winding of the transformer by a filter circuit. The switching element of the first power converter is shared by the switching element of the second power converter, and the first and second power converters are used. The inductance of each power conversion unit is set such that one of the currents flowing through the first power conversion unit is equal to or more than the critical current value and the other current is equal to or less than the critical current value, and the first voltage generated in the first power conversion unit Controlling the non-conducting period of the switching element according to the variation of the first voltage, thereby suppressing the variation of the first voltage, and controlling the conduction period of the switching element according to the variation of the second voltage generated in the second power converter. And a pulse width control means for controlling the fluctuation of the second voltage by controlling the switching regulator. 3. A rectifying circuit for rectifying an AC voltage, and a rectifying current generated in the rectifying circuit is chopped by controlling an energizing period of a switching element to generate a crossing current, and the crossing current is further converted to a choke coil and a capacitor. A first power converter that generates a first DC voltage by smoothing with a filter consisting of: and a capacitor output of the first power exchange unit is chopped by energizing period control of a switching element to reduce an intersecting current. A switching regulator having a second power converter that supplies a primary winding of a transformer and generates a second DC voltage by smoothing a voltage induced in a secondary winding of the transformer by a filter circuit. The switching element of the first power converter is shared by the switching element of the second current converter, and the first and second power converters The inductance of each power conversion unit is set so that one of the currents flowing through the first power conversion unit is equal to or more than the critical current value and the other current is equal to or less than the critical current value, and the first voltage generated in the first power conversion unit By controlling the on / off frequency of the switching element according to the fluctuation of the first element, the fluctuation of the first voltage is suppressed, and the conductivity of the switching element is controlled according to the fluctuation of the second voltage generated in the second power converter. A switching regulator comprising pulse width control means for suppressing a change in the second voltage by controlling a ratio between a period and a non-conductive period. 4. A rectifier circuit for rectifying an AC voltage, a chopping current generated by chopping a rectified current generated in the rectifier circuit by controlling an energizing period of a switching element, and further interchanging the chopping current with a choke coil and a capacitor. A first power conversion unit that generates a first DC voltage by smoothing with a filter consisting of: and a capacitor output of the first power conversion unit is chopped by controlling a conduction period of a switching element to reduce an intersecting current. A switching regulator having a second power converter that supplies a primary winding of a transformer and generates a second DC voltage by smoothing a voltage induced in a secondary winding of the transformer by a filter circuit. The switching element of the first power converter is shared by the switching element of the second power converter, and the first and second power converters are used. The inductance of each power conversion unit is set such that one of the currents flowing through the first power conversion unit is equal to or more than the critical current value and the other current is equal to or less than the critical current value, and the first voltage generated in the first power conversion unit By controlling the ratio of the conduction period and the non-conduction period of the switching element according to the fluctuation of the switching element, the fluctuation of the first voltage is suppressed, and the fluctuation of the second voltage generated in the second power converter is controlled. A switching regulator, comprising: a pulse width control unit that controls a change in a second voltage by controlling an on / off frequency of a switching element. 5. The switching regulator according to claim 1, wherein said pulse width control means uses a multiplication value of a voltage generated in said rectifier circuit and a first voltage generated in a first power conversion section. A switching regulator comprising means for stabilizing the first voltage of the first power conversion unit by controlling the power supply period of the switching device.