JPH10248247A - Boosting chopper circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a constant standby voltage with reference to a standby load by using a standby transformer in which a full-wave-rectified voltage is used as an input voltage and in which a chopper coil is used as a primary-side coil. SOLUTION: An input voltage Ein which is chopped by a switching FET 3 and which has a full-wave-rectified waveform is applied to a chopper coil L0 as the primary coil of a standby transformer 9a, and a rectified and smoothed voltage V1 whose waveform is similar to that of the input voltage Ein and whose waveform is changed is obtained by the secondary coil L1 having the number of turns N1 of the standby transformer 9a, by a switching diode 10 and by a smoothing capacitor 14. In addition, a rectified and smoothed voltage V2 whose waveform is opposite to that of the input voltage Vin and whose waveform is changed is obtained by the secondary coil L2 having the number of turns N2 (i.e., N2 =N1 ) identical to that of the secondary coil L2 of the standby transformer 9a, by a switching diode 13 and by a smoothing capacitor 15. The rectified and smoothed voltages V1 , V2 are added at the same polarity, and a standby voltage V3 at a constant voltage is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit of a color display device or the like, and more particularly to a power supply circuit using a step-up chopper to make a power factor of an AC power supply approach one.
The present invention relates to a boost chopper circuit of a so-called active filter type voltage converter.

[0002]

2. Description of the Related Art A step-up chopper circuit is applied to a voltage converter of an active filter system in which a power factor approaches 1. One example is described in JP-A-7-87744.

FIG. 4 is a circuit diagram showing a conventional example of an active filter type voltage converter using a boost chopper circuit, wherein 1 is an AC power supply, 2 is a bridge diode, 3 is a switch FET, 4 is a switching diode, 5 is a smoothing capacitor, 6 is a control circuit, 6a is a voltage dividing circuit, 6b is a reference voltage source, 6c is an error amplifier, 6d is a multiplier, 6e is an error amplifier, 6f is a pulse modulator, 7 is a load, and 8 is a current. The detection resistor L ₀ is a chopper coil.

[0004] In the figure, an AC AC power supply voltage V _in · sin [theta from the power supply 1a (where, θ = 0~π) is full-wave rectified by the bridge diode 1b, a voltage of the full-wave rectified waveform E _in E _in = V _in · | sinθ | is obtained. This voltage E _in the through chopper coil L ₀ of turns N _0, ON at a fixed frequency by the control circuit 6, OFF
Chopped by the controlled switching FET3,
The voltage is supplied to the smoothing capacitor 5 via the switching diode 4 to generate an output voltage V ₀ for the load 7.

When the switching EFT 3 is turned on, an input current i flows from the bridge diode 2 to the bridge diode 2 via the chopper coil L ₀ , the switching FET 3 and the current detecting resistor 8, and the chopper coil L
_When the power is stored in ₀ and the switching FET 3 is turned off, the power stored in the chopper coil L ₀ is released,
Switching diode 4 from the chopper coil L _0, the input current i to the chopper coil L ₀ flows through the smoothing capacitor 5 and the bridge diode 2, smoothing capacitor 5
Is charged.

The control circuit 6 detects the output voltage V ₀ obtained at the smoothing capacitor 5 and switches the switching FE accordingly.
By controlling the ON / OFF duty ratio of T3,
A constant predetermined output voltage V ₀ is obtained in the smoothing capacitor 5. Now, assuming that the ON period of the switching FET 3 is T _ON and the OFF period is T _OFF , generally, in the case of such a step-up chopper circuit, the output voltage V ₀ is V ₀ = E _in · (T _ON + T _OFF ) / T _OFF. in represented, even if the input voltage E _in is changed by the full-wave rectified waveform, the control circuit 6, a constant output voltage V ₀ is obtained.

Further, the control circuit 6, in the similar to the full-wave waveform of the input voltage E _in the waveform of the input current i is also performed operation to approximate the power factor to one.

That is, the output voltage V ₀ is divided by a voltage dividing circuit 6a at a fixed ratio to obtain a divided voltage, and an error voltage between the divided voltage and the reference voltage _Er from the reference voltage source 6b is converted to an error amplifier. amplified by 6c, this input voltage E _in the output voltage and the full-wave rectified waveform of the error amplifier 6c multiplied by the multiplier 6d, detects the output voltage and the input current i of the multiplier 6d by the current detection resistor 6e The error voltage from the detection voltage obtained by
e, a pulse signal having a constant frequency with a duty ratio corresponding to the error voltage is generated by a pulse modulation circuit 6f, and the switching signal is turned on by the switching FET 3 by this pulse signal.
N, OFF control.

[0009]

By the way, in a display device, as a countermeasure for power saving energy, the input power is set to about 5 W during a non-use time of a computer, so that a horizontal deflection circuit, a high voltage generation circuit, a video circuit, etc. are not required. It is equipped with a dedicated small standby transformer that cuts off power supply to the circuit and supplies power only to the microprocessor that controls the display device.

The additional addition of an active filter type booster chopper circuit including an expensive choke coil to such a display device leads to an increase in the number of components, an increase in mounting area, and an increase in cost.

In order to solve this problem, a transformer having a secondary coil magnetically coupled with a choke coil of an active filter type booster chopper circuit is provided. ), The conventional dedicated standby transformer may be deleted.

FIG. 5 is a circuit diagram showing an example of a voltage converter in which standby power can be obtained using such a transformer. 9 is a transformer, 10 is a switching diode, 10 is a smoothing capacitor, and 11 is a standby. load,
L ₁ is a secondary coil, the corresponding 4 and the description thereof is omitted here with the same reference numerals.

[0013] In the figure, the transformer 9, the chopper coil L ₀ of the the primary coil comprises a secondary coil L ₁ of a predetermined number of turns N ₁ which is magnetically coupled by winding the same bobbin and which It has a simple configuration. Voltage generated in the secondary coil L ₁ is rectified smoothed by the switching diode 10 and the smoothing capacitor 11, the standby loads 1
2 standby voltage V ₁ is obtained to be supplied to. Thus, even when the main load 7 such as a display device is not used and the switching FET 3 is turned on and the power is not supplied to the smoothing capacitor 5 during standby, power is supplied to the standby load 12 such as a microprocessor. I have to.

However, according to this voltage converter, when the switching FET 3 is turned on and off to supply power to the main load 7, the smoothing capacitor 11
There is a problem that the standby voltages V ₁ obtained does not become constant. Hereinafter, the operation of this voltage converter will be described with reference to FIG.

Assuming that the switching FET 3 is turned on and off to supply power to the main load 7, the input voltage Ein output from the bridge diode 2 becomes as shown _in FIG. , chopping has a full-wave rectified waveform, contrast, the voltage across the chopper coil L ₀ is the primary coil of the transformer 9, as shown in FIG. 6 (b), oN of the switching FET 3, the OFF operation The resulting waveform is obtained. In this case, the chopping waveform, as shown, consists of positive and negative pulses, the envelope of the pulse train of the positive electrode, similarly to the waveform of the input voltage E _in, increases with increase in the input voltage E _in, Although no waveform that decreases with decreasing input voltage E _in, the envelope of the negative polarity pulses, contrary to the waveform of the input voltage E _in,
It decreased with the increase of the input voltage E _in, input voltage E _in
Has a waveform that increases with the decrease of.

The voltage at both ends of the chopper coil L _{0 having} such a waveform is induced in the secondary coil L ₁ of the transformer 9 by multiplying it by N ₁ / N ₀ .
As shown in FIG. 6 (c), only a pulse voltage rectified into the positive waveform is obtained. This pulse voltage is smoothed by the smoothing capacitor 11, standby voltages V ₁ to thereby obtain, as shown in FIG. _{6 (d), V 1 =} V in · N 1 / N 0 · sinθ , and the input voltage waveform changes with the waveform change of E _in.

[0017] Thus, the input voltage E _in the in the voltage converter of the active filter method using the boost chopper circuit of the full-wave rectification waveform is not obtained constant standby voltage V _1.

An object of the present invention is to solve such a problem, and
To provide a step-up chopper circuit capable of obtaining a constant standby voltage when a standby coil is obtained using a standby transformer in which a secondary coil is a chopper coil to which an input voltage having a full-wave rectified waveform is supplied. is there.

[0019]

According to the present invention, a primary coil is a choke coil to which a full-wave rectified input voltage is supplied, and has a number of turns magnetically coupled thereto. A standby transformer provided with M coil pairs (where M is an integer of 1 or more) is provided with two secondary coils having the same value as a coil pair.
The induced voltage of the secondary coil is forward rectified and smoothed, and the induced voltage of the other secondary coil is flyback rectified and smoothed, and the respective rectified smoothed voltages are added with the same polarity.

The voltage obtained by the forward rectification smoothing is a voltage whose waveform changes like the input voltage, and the flyback rectification smoothing voltage is a voltage whose waveform changes inversely to the input voltage. Then, by adding the rectified and smoothed voltage to this with the same polarity, the waveform changes cancel each other, and a constant standby voltage is obtained.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an active filter type voltage converter using an embodiment of a boost chopper circuit according to the present invention, wherein 9a is a transformer, 13 is a switching diode, and 14 and 15 are smoothing capacitors. The same reference numerals are given to the portions corresponding to and the duplicate description will be omitted. FIG. 2 is a diagram showing voltage waveforms at various parts in FIG.

In the figure, a transformer 9a has a number of turns N _0.
The primary side coil is the chopper coil L of the step-up chopper circuit.
₀ and that is similar to the step-up chopper circuit shown in FIG. 5, the secondary coil L ₂ of the number of turns N 2 primary coil L ₁ of ₁ and turns N ₂ to the chopper coil L ₀ and the same bobbin It is of a simple configuration wound. However, these secondary coils L
₁ and L ₂ have winding directions opposite to each other and the number of windings N ₁ and N ₂
Are equal to N ₁ = N ₂ .

Now, the input voltage E _in of the full-wave rectified waveform output from the bridge diode 2 is changed as shown in FIG.
As shown in FIG. 6A, if E _in = V _in · | sin θ |, the voltage across the chopper coil L ₀ is as shown in FIG.
Similarly to FIG. 2B, as shown in FIG. 2B, a pulse voltage waveform is obtained in which a positive pulse voltage and a negative pulse voltage are alternately arranged. column of the envelope of the pulse voltage waveform, similar to the waveform of the input voltage _{E in, V in · | sinθ} | a and, also, the envelope of the column of the negative pulse voltage waveform due to the switching FET3 is turned OFF Is V ₀ −V _in · | sin θ |, contrary to the waveform of the input voltage E _in .

The secondary coil L _{1 of the} transformer 9a
2C, the rectifying action of the switching diode 10 induces a forward rectified voltage whose envelope is represented by (N ₁ / N ₀ ) · (V _in · | sin θ |). Is done. Further, from the secondary coil L ₂ of the transformer 9a, Figure 2
As shown in (d), the rectifying action of the switching diode 13 induces a flyback rectified voltage whose envelope is represented by (N ₁ / N ₀ ) · (V ₀ −V _in · | sin θ |). You.

When the forward rectified voltage is smoothed by the smoothing capacitor 14, a smoothed voltage V ₁ having substantially the same waveform as the envelope is obtained, and the flyback rectified voltage is smoothed by the smoothing capacitor 15. , the smoothed voltage V ₂ of almost the same waveform as the envelope is obtained, by which they are summed at the same polarity, as shown in FIG. _{2 (e), V 3 =} (N 1 / N 0) · V ₀ (where, N ₁ = N ₂ in which) will be constant standby voltage V ₃ is obtained.

[0026] Thus, in this embodiment, only it is not necessary to use a standby transformer, and also the input voltage E _in is a full-wave rectified voltage, the constant standby voltage V ₃ for standby load 12 It can be a voltage.

FIG. 3 is a circuit diagram showing an active filter type voltage converter using another embodiment of the step-up chopper circuit according to the present invention.
17 is a switching diode, 18 and 19 are smoothing capacitors, 20 is a switching FET, 21 is a switching transformer, 22 is a switching diode, 23 is a smoothing capacitor, and 24 is a control circuit, and the portions corresponding to those in FIG. A duplicate description will be omitted.

[0028] In the figure, the transformer 9b is the construction of the transformer 9a in FIG. 1, further secondary turns in reverse the direction winding the secondary coil L ₃ and this turns N ₃ is N ₄ with the addition of a coil L _4. These secondary coils L ₃ ,
L ₄ is a is wound to the primary coil L _0, 2 primary same bobbin coil L _1, L _2, the number of turns N _3, N ₄ is equally N ₃ = N _4.

[0029] Then, in the secondary coil L ₄ and the switching diode 16 and the smoothing capacitor 18, as in the secondary coil L ₁ and the switching diode 10 and the smoothing capacitor 14, the forward rectified smoothed voltage is obtained,
Moreover, secondary coils L ₃ and the switching diode 17
And in a smoothing capacitor 19, as in the secondary coil L ₂ and the switching diode 13 and the smoothing capacitor 15, the flyback rectification smoothed voltage is obtained by these rectification smoothed voltage that using addition of the same polarity, V _{4 = (N 3 / N 0} ) · V 0 ( where, N ₃ = N ₄₎ constant output voltage V ₄ is obtained.

The output voltage V ₄ is equal to the secondary coils L ₃ , L ₄
The number of turns N ₃ , N ₄ (where N ₃ = N ₄ ) is set as appropriate to be used as the power supply voltage for the control circuits 6 and 24. Thus, in this embodiment, the power supply voltages of the control circuits 6 and 27 can be obtained without using a dedicated power supply device.

A flyback switching circuit is provided between the smoothing capacitor 5 and the main load 7. That is, the switching circuit of the flyback system comprises a switching transformer 21 and a switching FET.
20, switching diode 22 and smoothing capacitor 2
And 3. The positive electrode of the smoothing capacitor 5 is connected to one terminal of the primary coil L _{5 having} the number of turns N ₅ of the switching transformer 21 as indicated by the symbol “・”, and the negative electrode of the smoothing capacitor 5 is It is connected to the other terminal of the 21 of the primary coil L _5. The secondary coil L ₆ having the number of turns N ₆ of the switching transformer 21 is wound in the opposite direction to the primary coil L 5. Are connected to the positive electrode of the smoothing capacitor 23 via the switching diode 22. The charging voltage E ₀ obtained at the smoothing capacitor 23 is supplied to the main load 7.

The control circuit 24 includes a switching FET 20
Is turned on and off at a constant frequency so that the output voltage V ₀ of the active filter type voltage converter is chopped and supplied to the primary coil L ₅ of the switching transformer 21. The output voltage E ₀ of the buck switching circuit is detected, and the ON / OFF duty of the switching FET 20 is adjusted so that the output voltage E ₀ becomes a constant predetermined voltage.

Here, the output voltage E ₀ of the flyback switching circuit is represented by V ₀ , the output voltage of the active filter type voltage converter, and the switching FET 20.
Assuming that the ON and OFF periods are T _ON and T _OFF , E ₀ = V ₀ · (T _ON / T _OFF ) · (N ₆ / N ₅ ).

As described above, in this embodiment, the two secondary coils magnetically coupled to the primary coil are used as a coil pair, and the coil pair is used as the standby load 8 and the control circuit 6.
By providing every 24, a constant power supply voltage can be obtained for each of the transformers 9b having the same bobbin.

In this embodiment, a constant predetermined power supply voltage is always supplied to the standby load 8 and the control circuits 6 and 24. However, when the control circuits 6 and 24 need different power supply voltages. , Each having two 2
Each power supply voltage can be generated by providing a secondary coil or the like, and in general, a standby load that requires application of M (where M is an integer of 1 or more) constant power supply voltages (this standby load is , And a control circuit), two secondary coils each having the same predetermined number of turns are provided in the transformer 9b in the same manner as described above, and the forward rectified smoothed voltage and the flyback rectified smoothed voltage are respectively provided for each of them. By generating and adding them with the same polarity, it is possible to obtain a constant predetermined power supply voltage for each standby load.

[0036]

As described above, according to the present invention,
By using a transformer having a simple configuration having a coil magnetically coupled with a choke coil, a dedicated and expensive standby transformer is not required, and a constant standby voltage can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a boost chopper circuit according to the present invention.

FIG. 2 is a diagram showing voltage waveforms at various parts in FIG.

FIG. 3 is a circuit diagram showing another embodiment of the boost chopper circuit according to the present invention.

FIG. 4 is a circuit diagram showing an active filter type voltage converter to which a conventional boost chopper circuit is applied.

FIG. 5 is a circuit diagram showing a configuration in which standby power extraction means is provided in the conventional example shown in FIG. 4;

FIG. 6 is a diagram showing voltage waveforms at various parts in the voltage converter shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 AC power supply 2 Bridge diode 3 Switching FET 4 Switching diode 5 Smoothing capacitor 6 Control circuit 7 Main load 8 Current detection resistor 9a, 9b Standby transformer 10 Switching diode 12 Standby load 13 Switching diode 14, 15 Smoothing capacitor 16, 17 Switching diode 18 , 19 Smoothing capacitor 20 Switching FET 21 Switching transformer 22 Switching diode 23 Smoothing capacitor 24 Control circuit

Claims (3)

[Claims] 1. A step-up chopper circuit in which a voltage of a full-wave rectified waveform is used as an input voltage, and the input voltage is chopped and supplied to a chopper coil, wherein two booster chopper coils magnetically coupled to the chopper coil have the same number of turns. A coil is a set of coil pairs, and M coil pairs (where M is an integer of 1 or more) are provided. For each of the coil pairs, the induced voltage of one of the coils in the same coil pair is forward rectified. Smoothing to obtain a first rectified smoothed voltage, flyback rectifying and smoothing the induced voltage of the other coil to obtain a second rectified voltage, and adding the first and second rectified smoothed voltages with the same polarity. A boost chopper circuit characterized in that the boost chopper circuit supplies the voltage to a load. 2. The step-up chopper circuit according to claim 1, wherein two coils forming the same coil pair have the same number of turns. 3. The step-up chopper circuit according to claim 1, wherein each coil of the M coil pairs is wound around the same bobbin as the chopper coil to form a transformer.