JPH04162112A - Multi-output power supply circuit - Google Patents

Abstract

PURPOSE:To apply a voltage to one of two power supplies even though the other power supply does not rise up to a prescribed level by adding an overload detecting transistorTR and a current mirror circuit to the multi-output power supply circuit. CONSTITUTION:In this multi-output power supply circuit, the base and the emitter of an NPN TR 37 are connected to the base and the emitter of an NPN TR 9 respectively and the collector of the TR 37 is connected to the collector and the base of a PNP TR 38 serving as the input side of a current mirror circuit and also connected to the base of a PNP TR 39 respectively. Each emitter is provided with a circuit where the output of a PNP current mirror circuit connected to a power terminal 27 is connected to the output of a 1st comparator which decides the sequence of the 1st and 2nd power supply circuits. The overcurrent of the power supply circuit is detected by the TR 37 before the voltage V1 rises up to a prescribed level. Then the TR 14 and 15 are turned on and the output voltage V2 rises.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an integrated power supply circuit having multiple outputs, and particularly to a multiple output circuit in which two outputs are activated in sequence when the power supply voltage increases. Regarding power supply circuits.

[Conventional technology]

FIG. 3 is a circuit diagram of a conventional integrated multiple output power supply circuit, and FIG. 4 shows the power supply voltage and output terminal voltages V, v, in FIG.
FIG. 2 is a characteristic diagram showing the relationship of No. 2 when the load is light and when the load is heavy.

This multiple output power supply circuit has two power supply circuits with output voltages V, V2. The first power supply circuit connects a reference voltage source 11 to a non-inverting input and an output terminal 2 to a resistor 3.4 to an inverting input.
and a first error amplifier 6 to which the feedback voltage divided by the resistor 5 is input, an NPN transistor 7 as an output transistor, and a resistor 8 for the current limit circuit. The second power supply circuit is composed of an NPN transistor 9, and includes a reference voltage source 11 at its non-inverting input, a second error amplifier 13 which receives a feedback voltage divided by a resistor 11 and a resistor 12 from an output terminal 10 at its inverting input, and an output. The transistor is composed of NPN transistors 14 and 15 and a resistor 16, and the NPN transistors 14 and 15 are connected in Darlington and have a common collector connected to the base terminal 18 of an external PNP transistor 17.

Furthermore, in order to start up the pressure terminal 2 and the output terminal 10 in sequence, the reference voltage source 1. A first comparator 19 inputs a feedback voltage divided by a resistor 3 and a resistor 4.5 from the output terminal 2 to its non-inverting input, and the base of an NPN transistor 20a whose emitter is grounded is connected to the output of this comparator 19. The collector is connected from the reference voltage source 1 through a resistor 22 to the intersection between the bases of the emitter-grounded NPN transistors 24 and 25 and the collector of the emitter-grounded NPN l-transistor 26. The base of is biased from the reference voltage source 1 through a resistor 21 and a diode-connected NPN transistor 23, and the first power supply circuit is connected to the first power supply circuit, in which the collector of the NPN transistor 25 is connected to the output of the second error amplifier. After the voltage at the power supply terminal 27 increases, the emitter for shorting the output terminal 2.10 is connected to the output terminal 10.1. Connect the base to the base terminal 30. External PNP with collector as output terminal 2)
- transistor 29 and output terminal 1 for driving it
0 through a resistor 31, the base is connected to a grounded emitter NPN (NPN) transistor 32, and a current limiting resistor 33.

Next, the operation of this multiple output power supply circuit will be explained.6 The voltage at the output terminal 2 is the voltage obtained by dividing the voltage at the reference voltage source 1 and the output terminal 2 by the resistor 34 and the resistor 5, as in a normal constant voltage circuit. are compared by the error amplifier 6 and set as a constant output,
Similarly, the voltage at the output terminal 10 is a constant output. Also, the circuit that operates the first power supply circuit first is the NP
NPN transistors 26 and 24 constitute a latch circuit, and the NPN transistor 25 operates only when the power supply voltage rises, sets the output of the second error amplifier to low level, stops the operation of the second power supply circuit, and lowers the output terminal 10 to low level. It is said that

When the power supply voltage is applied as shown in section A in Figure 4<a), the voltage of the resistor divider of the output terminal 2 is lower than the reference voltage 1 and the output of the first comparator is low, and the NPN transistor 20 also remains FF. Then, the NPN) transistors 25 and 24 turn on before the NPN transistor 26, and the output of the second error amplifier circuit becomes low, the output terminal 10 becomes low, and the resistor 31
Since the NPN) transistor 32 is not biased, with the external PNP) transistor 17 also turned off,
Only the first power supply circuit is operating.

Next, as shown in section B of FIG. 4 (a>), the power supply voltage 28 is
When the voltage rises sufficiently and the resistor-divided voltage at output terminal 2 exceeds reference voltage source 1, the output of the first comparator is inverted to high.
NPN) transistor 20 is turned on, NPN) transistors 25 and 24 are turned off, and NPN transistor 26 is turned on, thereby latching the power supply voltage and lowering the voltage of reference voltage source 1 to about (1.4 or less). NPN) The transistor 26 remains in the ON state and continues to hold the latched state until the NPN) becomes low. At this time, when the NPN) transistor 25 is turned off, the second power supply circuit operates normally, and the output terminal 10 is set to a constant voltage, and the resistor 31 turns on the NPN) transistor 32 to saturate it, and the current is limited by the resistor 33. , the external PNP) - transistor 29 is turned on and saturated, and the voltage at the output terminal 2 is increased to a voltage lower than the voltage at the output terminal 10 by the saturation voltage, and the voltage at the output terminal 2゜'10 is Make them equal.

At this time, when the output terminal 10 becomes abnormal and an overcurrent flows as in section C, the overcurrent is detected by the resistor 34, the output of the error amplifier 13 is set to low by the protection circuit 35, and the voltage 2 of the output terminal 10 falls. At this time, the potential of the output terminal 2 of the first power supply circuit also decreases, but the output voltage determined by the division ratio of the resistor 3.4 and the resistor 5 is maintained. The second power supply circuit operates independently.

When the power supply voltage decreases and approaches voltage v2 as in section D, negative feedback is no longer applied to the second power supply circuit, and V2 at the output terminal 10 becomes a voltage that is the numerator of the saturation voltage of the PNP transistor 17 from the power supply voltage. , (1) is processed using a voltage that is the numerator of the saturation voltage of the PNP transistor 29 from v2.

In this way, this power supply circuit can sequentially output V 1 and V 2 from the output terminals 2 and 10 when the power is turned on, so it can be used as a power supply circuit for a system using a microcomputer, memory, etc. to prevent malfunctions when the power is turned on. It can be prevented.

[Problem to be solved by the invention]

The conventional multiple output power supply circuit described above has a built-in circuit that operates the first power supply circuit first when the power supply voltage rises, so the first power supply circuit operates and
Since the second power supply circuit is designed to operate when the voltage rises to a specified voltage, as in No. 41g(b),
When the output terminal 2 does not rise to the specified voltage due to overload, the second power supply circuit does not operate even if the power supply voltage rises sufficiently, and the output terminal 10 (2) remains in the low state, and the output terminal 10 The disadvantage is that voltage cannot be supplied to the connected load circuit.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks and provide a multi-output power supply circuit that can output voltage to the other power supply even when one power supply does not rise to a specified value.

[Means to solve the problem]

The configuration of the multiple output power supply circuit of the present invention is such that the difference between the voltage obtained by dividing the first output voltage by the first feedback circuit and the reference voltage is amplified and the output voltage is increased by driving the first output transistor. a first power supply circuit that obtains a second output voltage by driving a second output transistor; The voltage from the feedback circuit and the reference voltage are compared by a comparator, and the output thereof is supplied to the base of the second output transistor through a latch circuit. A multi-output power supply circuit including a power supply control circuit that operates the circuit first, a first transistor that detects an overcurrent in the first power supply circuit, and a first transistor that is driven by the output of the first transistor. A second transistor of opposite conductivity type. and a current mirror circuit consisting of a third transistor, and the output of the current mirror circuit is connected to the output terminal of the comparator so that the second power supply circuit can be driven independently of the first power supply circuit. It is characterized by what it did.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

Fig. 1 is a circuit diagram of an integrated multiple output power supply circuit according to an embodiment of the present invention, and Fig. 2 shows the power supply voltage and output voltage V of Fig. 1.
,,V2, and FIG. 2(a) is a diagram when the load connected to the output terminal 2 is light, and FIG. 2(b) is a diagram when the load is heavy.

This power supply circuit differs from the conventional circuit in that it includes an NPN transistor 37 whose base and emitter are connected to the base and emitter of an NPN transistor 9, and the collector side of this NPN transistor 37 is the input side of a current mirror. Collector-base of PNP transistor 38 and PNP
) to the base of the transistor 39, and each emitter connects the output of a PNP type current mirror connected to the power supply terminal 27 to the first . The first circuit determines the ordering of the second power supply circuit.
It is equipped with a circuit connected to the output of the comparator.

The operation of this circuit is the same as that of the conventional example, but when the power is turned on, the output terminal 2 becomes abnormal and an overcurrent flows, as shown in section A in Figure 2 (b), or a microcomputer or the like causes a momentary large current to flow. When the voltage vl does not rise to the specified voltage due to
The NPN transistor 37 detects an overcurrent in the power supply circuit of
4 is turned off, the NPN transistor 26 is turned on and becomes a latch state, the output of the second error amplifier 13 becomes high, the NPN transistors 14 and 15 are turned on, and the voltage 2 of the output terminal 10 rises. Note that the subsequent operation is the same as in the conventional example.

〔Effect of the invention〕

As explained above, the present invention adds an NPN (NPN) transistor for detecting overload of the first power supply circuit and a PNP transistor of the current mirror circuit to the conventional multiple output power supply circuit, so that when the power is turned on, the output terminal is If an abnormality occurs and an overcurrent flows, or a microcontroller causes a momentary large current to flow,
Even if V6 does not rise to the specified voltage of the first power supply, the second power supply circuit can be operated to increase the output voltage, which has the effect of supplying voltage to subsequent circuits.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a multiple output power supply circuit according to an embodiment of the present invention, and Fig. 2 (a>, (b) shows the relationship between the power supply voltage and the output terminals V, V2 in Fig. Figure 3 is a circuit diagram of an example of a conventional integrated multiple output power supply circuit, Figures 4 (a) and (b) are the power supply voltage and output terminal voltage in Figure 3. It is a characteristic diagram showing the relationship with V,, V2 when the load is light and when the load is heavy. 1... Reference voltage source, 2.10... Power supply output terminal (V
+, V2>, 5~5, 8.11, 12.16°21
．． 22, 31, 33, 34.40...Resistance, 6.13
...Error amplifier, 7, 9, 14, 15°20.24~
26, 32.37...NPN transistor, 17.2
3,29,38.39...PNP transistor, 18
．． 30... Base terminal, 19... Comparator, 27...
- Power supply terminal, 28...Power supply voltage source, 35...Overcurrent protection circuit, 36...Grounding terminal.

Claims (1)

[Claims] a first power supply circuit that obtains the output voltage by amplifying the difference between a voltage obtained by dividing the first output voltage by a first feedback circuit and a reference voltage and driving the first output transistor; a second power supply circuit which is provided in parallel with the same configuration as the first power supply circuit and obtains a second output voltage by driving a second output transistor; and a voltage from the first feedback circuit and the reference voltage. and a power supply control circuit that operates the first power supply circuit first when the power supply voltage rises by comparing the output with a comparator and supplying the output to the base of the second output transistor through a latch circuit. In the multi-output power supply circuit, a first transistor detects an overcurrent in the first power supply circuit, and second and third transistors are driven by the output of the first transistor and have a conductivity type opposite to that of the first transistor. A current mirror circuit consisting of a transistor is provided, and the output of the current mirror circuit is connected to the output terminal of the comparator so that the second power supply circuit can be driven independently of the first power supply circuit. Features multiple output power supply circuit.