JPS627773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC stabilized power supply circuit.

Conventionally, series regulators have been widely used as DC stabilized power supply circuits due to their excellent stability and low output voltage ripple.
It has the drawbacks of low efficiency and large power loss due to series transistors. For this reason,
Today, DC voltage is controlled on and off,
There is a tendency to use efficient switching regulators that control the output voltage based on the ratio of on time to off time.

Generally, as this type of switching regulator, for example, a current source switching regulator having a circuit configuration shown in FIG. 1 is known.
That is, the switching regulator shown in FIG. 1 includes an inverter circuit INV in which switching elements Tr ₁ to _{Tr 4} such as transistors are bridge-connected for DC current E, and a transformer T at the AC output side terminal of this inverter circuit INV. A rectifier circuit in which rectifying elements D ₁ to _{D 4} such as diodes are connected via a bridge.
The DC output terminal side of the rectifier circuit REC is connected to the load via an output filter consisting of a smoothing reactor L and a smoothing capacitor C.
Ld is connected, the voltage applied to this load Ld side is detected, and each switching element Tr ₁ to _{Tr 4} of which constitutes the inverter circuit INV is detected based on this voltage detection value and the voltage command value from the voltage command device. The configuration is such that the conductivity is controlled to keep the output voltage to the load Ld constant. The circuit for controlling the conductivity can be composed of a voltage detector VD, a voltage command VC, a comparison amplifier A, and a conductivity regulator CR connected to the DC output side terminal of the rectifier circuit REC. . In addition, on the primary winding side of the transformer T,
A capacitor Cp for preventing biased magnetism is connected.

In a conventional switching regulator configured in this way, for example, when the switching frequency is 20KHz, the resonant frequency of the output filters L and C is approximately two orders of magnitude higher than the switching frequency in order to sufficiently reduce the output voltage ripple. Reduce to about 200
It is generally set as Hz. Therefore, in order to avoid the resonance point set in this way, the response frequency of the constant voltage control system is set to 100 Hz or less, and the response delay time is set to 5 ms or more. Therefore, if you want to improve the response speed, you can increase the switching frequency above 20KHz, but there is a limit due to increased switching loss, etc., so the transient response characteristics to disturbances such as sudden changes in load may not match the series level. It has the disadvantage of being inferior to Yureta.

In addition, in conventional switching regulators, due to variations in the characteristics of the switching elements Tr ₁ to _{Tr 4} , a slight DC component is generated in the primary winding of the transformer T, causing the transformer T to be biased, resulting in excessive magnetization. Since there is a risk that the excitation current may flow and damage the switching elements _Tr1 to _Tr4 , it is necessary to provide overcurrent prevention means such as a capacitor Cp for preventing biased magnetism, as shown in FIG.

Furthermore, in conventional switching regulators, when obtaining an ultra-high output voltage, a large charging/discharging current flows due to the stray capacitance of the secondary winding of the transformer T, and the switching elements Tr ₁ -
In order to cause a large inrush current to flow through Tr ₄ , it is necessary to use a special transformer that can set the strain capacitance to an extremely small value.

As mentioned above, conventional switching regulators have excellent characteristics in terms of efficiency, but they also have many drawbacks in terms of response characteristics and manufacturing, and they also have drawbacks such as extremely limited range of application. Ta.

Therefore, the inventors of the present invention have conducted various studies in order to overcome all the problems of the conventional switching regulator mentioned above. The output current value is always controlled to be constant, and this direct current is converted into alternating current by a bridge-connected switching element while creating a partial bypass period, and the converted current is transmitted to the rectifier/smoothing circuit via a transformer. By doing so, the smoothing reactor of the output filter can be omitted, and the transient response speed can be improved as the switching frequency is improved, and the problems of conventional switching regulators can be solved at once. I found out.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a switching regulator that can significantly improve the response characteristics, which have been considered a drawback of conventional switching regulators, and is easy to manufacture.

In order to achieve the above object, in the present invention, a constant DC current supplied from a constant current source is
A bridge-connected switching element converts the current into alternating current while partially creating a bypass period, and transmits the converted current to the rectifying/smoothing circuit via the transformer. The present invention is characterized in that a desired DC output voltage can be obtained from the rectifying/smoothing circuit by adjusting the time ratio between the period during which the DC output voltage is converted and introduced into the transformer.

In the switching regulator described above, the constant current source that supplies a constant DC current can be constructed by connecting a voltage-current conversion circuit to a DC power source. In this case, the voltage-current conversion circuit can be constructed of a series circuit of a switching element and a diode, and the current can be drawn out via a reactor using both terminals of the diode as a current source.

Next, embodiments of the switching regulator according to the present invention will be described in detail below with reference to the accompanying drawings.

In the embodiment shown in FIG. 2, switching elements 10a to 10d consisting of transistors are connected to a DC power supply 12
an inverter circuit 10 bridge-connected to the
It consists of a transformer 14 connected to the AC output side terminal of the inverter circuit 10, and a diode rectifier circuit 16 bridge-connected to the secondary winding side of the transformer 14. A load 20 is connected through an output filter consisting of a smoothing capacitor 18, and the input voltage of the load 20 is detected by a voltage detector 22, and this voltage detection value is compared and amplified with a command value of a voltage command device 24 by an amplifier 26. Each switching element 10 of the inverter circuit 10 via the conductivity regulator 28
The circuit is basically configured to adjust the conductivity of a to 10d and control the output voltage to the load 20 to be constant. This basic circuit configuration is substantially the same as that of the conventional switching regulator shown in FIG.

In the circuit of this embodiment, a voltage-current conversion circuit 30 is provided between the DC power supply 12 and the inverter circuit 10 to supply a constant DC current to the inverter circuit 10, and the switching elements 10a to 10d of the inverter circuit 10 It is characterized in that it is converted into alternating current while partially causing a bypass period. That is, the voltage-current conversion circuit 3
0 is a switching element 3 connected in series with the DC power supply 12.
A diode 34 is connected in parallel to the series circuit of the DC power supply 12 and the switching element 32, and a constant current is applied to the input side terminal of the inverter circuit 10 via a reactor 36 between both terminals of the diode 34. It is connected as a source. Note that the switching element 32 is a diode 3
Current detector 3 detects the current flowing to the output side of 4.
The conductivity is adjusted by a feedback control circuit consisting of a current command unit 8, a current command unit 40, and a conductivity regulator 42, and the output current is controlled to be substantially constant.

Next, the operation of the switching regulator according to the present invention constructed as described above will be explained based on the operation waveform diagram shown in FIG.

As is clear from the circuit configuration described above, the voltage-current conversion circuit 30 used in this embodiment acts as a constant current source for the inverter circuit 10. First, the output current value i ₃₀ of the voltage-current conversion circuit 30 is set as shown in FIG. 31. Further, when the conductivity adjustment characteristic e ₂₈ of the conductivity regulator 28 and the output voltage e ₂₉ of the amplifier 26 are set as shown in FIG.
Each switching element 10a of the inverter circuit 10
The output signal ea of the conductivity regulator 28 for ~10d
~ed becomes as shown in FIG. 3.

In this way, in the inverter circuit 10, the bridge-connected switching elements 10a
10d, a constant direct current supplied from a constant current source is converted into an alternating current while partially creating a bypass period, and is transmitted to the transformer 14. In this case, the time ratio between the period during which the DC current is bypassed and the period during which the DC current is converted into AC current and guided to the transformer 14 is adjusted as shown in FIG. 3 and 4. That is, the third
The waveform shown in FIG. 4 shows the output of the inverter circuit 10, that is, the primary current i ₁₄ of the transformer 14. In this way, the diode rectifier circuit 16 and the smoothing capacitor 18 are connected via the transformer 14.
The output current i ₁₈ and the output voltage e ₂₂ supplied to the load 20 side through the circuit are as shown in FIGS. 3, 5 and 6, respectively, and the output voltage e ₂₂ is controlled to be substantially constant.

In this example circuit, the response frequency for controlling the output voltage e ₂₂ to be constant is approximately the same according to the automatic control theory and the experimental results, and the switching frequency is = 1/T (Hz) [Fig. [Reference]] was confirmed. Also, the response delay time is τ≒T/
2 (sec) [see Fig. 3, 5]. That is, if the switching frequency f is set to 20 KHz, the response frequency will also be 20 KHz, and the response delay time in this case will be approximately 25 μs.

As is clear from the embodiments described above, according to the switching regulator of the present invention, by providing a constant current source consisting of a voltage-current conversion circuit on the power supply side of the inverter circuit, it is possible to eliminate the need for a conventional output filter. This eliminates the need to install a smoothing reactor, and also improves transient response speed by approximately 200 times compared to conventional switching regulators. That is, the response frequency can be improved from 100Hz to 20KHz, and the response delay time can be improved from 5ms to 25μs.

Note that in the embodiment shown in FIG.
6 is directly connected to the conductivity regulator 38 of the voltage-current conversion circuit 30, and the conductivity regulator 28 of the inverter circuit 10
By configuring the current source circuit as a simple 180° conduction command device to actively adjust and control the current source circuit,
Although the configuration of the control circuit is simplified, it has been confirmed that in this case no improvement in response speed as described above can be expected.

In addition, in the present invention, by using a constant current source as the input of the inverter circuit, no overcurrent occurs even if biased magnetization occurs in the transformer, so there is no need for a bias prevention means for the transformer as in the past. There is.

Furthermore, it is very advantageous for the stray capacitance of the transformer winding, which makes it easy to realize DC stabilized power supply circuits for ultra-high voltages.In particular, since it is transformer-coupled, it is extremely advantageous for the stray capacitance of the transformer winding. It can be suitably applied as a highly accurate DC stabilized power supply circuit.

Furthermore, as a means for obtaining a current source, a current source such as a fuel cell or a solar cell can be directly used instead of a voltage-current exchange circuit, so that the switching regulator according to the present invention has a wide range of applications.

Although the preferred embodiments of the present invention have been described above, it goes without saying that various design changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional switching regulator, Fig. 2 is a circuit diagram showing an embodiment of a switching regulator according to the present invention, and Figs. 3 1 to 6 are the circuits shown in Fig. 2. FIG. 10... Inverter circuit, 10a to 10d...
Switching element, 12... DC power supply, 14...
Transformer, 16...Diode rectifier circuit, 18...
... Smoothing capacitor, 20 ... Load, 22 ... Voltage detector, 24 ... Voltage command device, 26 ... Amplifier,
28...Conductivity regulator, 30...Voltage/current conversion circuit, 32...Switching element, 34...Diode, 36...Reactor, 38...Current detector, 40...Current command device, 42...Continuity rate adjuster.

Claims (1)

[Claims] 1. A constant DC current supplied from a constant current source,
A bridge-connected switching element converts the current into alternating current while partially creating a bypass period, and transmits the converted current to the rectifying/smoothing circuit via the transformer. A switching regulator characterized in that a desired DC output voltage is obtained from the rectifier/smoothing circuit by adjusting the time ratio between the period during which the DC output voltage is converted and introduced into a transformer. 2. A switching regulator according to claim 1, in which the constant current source is configured by connecting a voltage-current conversion circuit to a DC power source.