JPH0530177Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to a DC power supply device that generates a high DC voltage by connecting three terminal regulators in series.
In particular, it relates to improving start-up characteristics.

(Prior Art) FIG. 5 is a circuit diagram of a device in which two conventional three-terminal regulators are connected in series. In the figure, the 3-terminal regulator IC1 stabilizes the input voltage V1 and outputs the output voltage Vout1.
2 stabilizes the input voltage V2 and outputs the voltage Vout2
Output. Since the ref terminal of the three-terminal regulator IC1 is connected to the out terminal of the three-terminal regulator IC2, these output signals Vout3 satisfy the following equation.

Vout3=Vout1+Vout2 (1) The three-terminal regulator IC2 has a built-in overcurrent protection circuit, such as a fold-back type, to prevent damage due to overload. Here, what is the fold-back hanging type?
In a graph with output voltage on the horizontal axis and output voltage on the vertical axis, both the output voltage and output current decrease when the output exceeds the rated value, and it is called this because the solid resembles a fu. Capacitor C1 stores output signal Vout3, and capacitor C2 stores output voltage Vout2. The diode D is connected between the out terminal and the ref terminal of the three-terminal regulator IC2, and prevents the reverse bias voltage from exceeding a predetermined voltage Vf, thereby preventing damage to the three-terminal regulator IC2.

(Problems to be Solved by the Invention) However, the conventional device has the following disadvantages because the overcurrent protection circuit is built into the three-terminal regulator. In other words, 3-terminal regulator IC
When the rise of voltage Vout2 is slower than that of the three-terminal regulator IC1, a current i1 due to the output voltage Vout1 of the three-terminal regulator IC1 flows in the direction shown by the broken line in the figure. As a result, capacitors C1 and C2
is charged to the polarity shown in the figure. At this time, the voltage across the terminals of capacitor C2 is 3-terminal regulator IC2.
A reverse bias state is created between the out terminal and the ref terminal of the 3-terminal regulator IC2, and the overcurrent protection circuit of the 3-terminal regulator IC2 remains activated.
There was a problem that 2 did not start up. Of course,
A diode D is inserted, but this is for preventing damage to the three-terminal regulator, and does not inhibit the operation of the overcurrent protection circuit.

This invention solves these problems,
To provide a DC power supply device that reliably starts up in a normal state even if there is a difference in start-up time between three-terminal regulators connected in series.

(Means for Solving the Problems) The present invention that achieves the above object has a first input voltage inputted between an input terminal and a reference terminal, and a first output voltage Vout1 outputted to an output terminal. 1, a 3-terminal regulator, and a 2nd 3-terminal regulator, which inputs a second input voltage between the input terminal and the reference terminal and outputs the second output voltage Vout2 to the output terminal.
a first capacitor C1 having a terminal regulator and inserted between the output terminal of the first three-terminal regulator and the reference terminal of the second three-terminal regulator and supplying the sum of the first and second output voltages; , a second capacitor C2 having one end connected to the reference terminal of the first three-terminal regulator and the second three-terminal regulator and the other end connected to the reference terminal of the second three-terminal regulator.
This is a DC power supply device having the following configuration.

That is, the second three-terminal regulator is equipped with a fold-back overcurrent protection circuit, and a bias voltage Vb given by the following equation is supplied to the output terminal of the second three-terminal regulator via a diode. This is a characteristic feature.

{C1/(C1+C2)}・Vout1<Vb<Vout2 (Function) Each component of the present invention has the following function. The bias voltage overcomes the reverse bias voltage of the first three-terminal regulator, which rose first, suppresses the operation of the overcurrent protection circuit, and secures the rising of the second three-terminal regulator.

(Example) The present invention will be explained below using the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, parts having the same functions as those in FIG. 5 are given the same reference numerals and their explanations will be omitted. In the figure, Db is a diode with one end connected to the bias voltage Vb and the other end connected to the output terminal of the three-terminal regulator IC2, and the polarity is determined so that the current does not flow backward toward the bias voltage side. The bias voltage is determined to satisfy the following equation.

{C1/(C1+C2)}·Vout1<Vb<Vout2 (2) The operation of the device configured as described above will be described next. FIG. 2 is a state diagram showing the flow of signals.

When the power is turned on, if the rise of the 3-terminal regulator IC2 is later than that of the 3-terminal regulator IC1,
Due to the stabilized output Vout1 of the three-terminal regulator IC1, a current i1 flows through the path shown by the dotted line in the figure.
Then, the capacitors C1 and C2 are charged with the polarity shown in the figure by the current i1, and the three-terminal regulator
The voltage between the reference terminal and the output terminal of IC2 is reverse biased to the following voltage.

−{C1/(C1+C2)}・Vout1 (3) This causes the overcurrent protection circuit of the three-terminal regulator IC2 to operate.

When the bias voltage Vb is supplied here, this reverse bias state is canceled from the relationship between equations (2) and (3). Therefore, the 3-terminal regulator IC2 comes out of the overcurrent protection state and this output voltage becomes
Increases to Vout2.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. Here, the bias voltage is obtained not from the outside but by dividing the input voltage V2 by resistors R1 and R2. Note that the voltage division ratio is determined so that the bias voltage satisfies equation (2).

FIG. 4 is a circuit diagram showing a third embodiment of the present invention. Here, 3-terminal regulator IC1, IC2
Both of these cases show cases in which a fold-back droop type overcurrent protection circuit is built-in. Smoothing capacitor C
3 and C2 are inserted between the reference terminal and output terminal of the three-terminal regulators IC1 and IC2.

In this case, the 3-terminal regulator that rises slowly remains in the overcurrent protection state, and
Unable to stand up properly. At this time, bias voltage is applied to both output terminals of the 3-terminal regulator IC1 and IC2 via diodes Db1 and Db2.
Supply Vb1 and Vb2. Then, the bias voltage
Vb1 and Vb2 prevent the occurrence of a reverse bias state, allowing normal startup.

(Effects of the invention) As explained above, according to the invention, even if there is a difference in the rise time of the three-terminal regulators connected in series, the bias voltage Vb allows the fold-back droop type overcurrent protection circuit to operate. Since the operation can be suppressed, this has the practical effect of making reliable startup possible.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
3 is a state diagram showing the flow of signals, FIG. 3 is a circuit diagram showing a second embodiment of the present invention, and FIG. 4 is a circuit diagram showing a third embodiment of the present invention. FIG. 5 is a circuit diagram of a conventional device. IC1, IC2...3 terminal regulator, C1,
C2...Capacitor, Db...Diode, Vb...
...bias voltage.

Claims (1)

[Claims for Utility Model Registration] A first input voltage is input between the input terminal and the reference terminal, and a first output voltage Vout1 is input to the output terminal.
A first three-terminal regulator outputs Vout2, a second input voltage is input between the input terminal and the reference terminal, and a second output voltage Vout2 is input to the output terminal.
a second three-terminal regulator that outputs a voltage of a second capacitor C2 having one end connected to the reference terminal of the first three-terminal regulator and the second three-terminal regulator and the other end connected to the reference terminal of the second three-terminal regulator; In the DC power supply device, the second three-terminal regulator is equipped with a fold-back overcurrent protection circuit, and a bias voltage is applied to the output terminal of the second three-terminal regulator via a diode as shown in the following equation. A DC power supply device characterized by supplying Vb. {C1/(C1+C2)}・Vout1＜Vb＜Vout2