JPH0454826A - Power supply output circuit - Google Patents

Abstract

PURPOSE:To facilitate setting of a reference voltage for prescribing sequences of main output and suboutput by turning the suboutput ON/OFF in response to abrupt variation of output from an error amplifier being employed in feedback control of the main output. CONSTITUTION:When power is thrown in and the output voltage V01 reaches a predetermined level, output voltage from an error amplifier 7 goes abruptly to some level and a feedback control is carried out so that the voltage V01 at an output terminal 4 will be constant. The abrupt variation is detected through a voltage detector 14 and a power supply 15 functions to rise the output voltage V02 at terminal 5 with a lag. In other words, the output voltage V02 rises when the output e1 exceeds the reference voltage of the voltage detector 14. Upon interruption of power supply, output voltage at the terminal 4 can not be maintained constant even through the feedback control and the output of the error amplifier 7 varies abruptly when a stable output range is exceeded. The voltage detector 14 detects the abrupt variation and turns the power supply 15 OFF thus falling the output voltage.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a power output circuit, and in particular has multiple power outputs,
This invention relates to a power supply output circuit that has a sequence in the rise and fall of these outputs.

BACKGROUND ART In general, in circuits that require two types of power supplies, it may be necessary to define a sequence for turning on and off the two power supplies in order to maintain bias on the circuit. For example, there are low voltage and high voltage, and their high-low relationship is always maintained,
There are circuits that require prevention of current backflow and protection from circuit malfunction. Furthermore, it may be necessary to specify the order in which voltages rise when initializing a circuit such as when power is turned on.

Conventionally, a power supply output circuit for regulating this kind of voltage sequence monitors the output voltage that rises first, detects that the output voltage has reached a certain voltage value, and uses the detected output to The power supply circuit for the output voltage to be turned on was driven to start up the power supply. Then, when turning off the device, the reverse operation is performed to define the sequence of rise and fall of the output voltage.

The conventional power output circuit will be explained using FIG. 3. FIG. 3 is a circuit diagram showing the configuration of a conventional power output circuit.

In the figure, terminals 1 and 2 are power input terminals, and an input voltage Ein is applied between these terminals 1 and 2. The power converter 3 that receives the input voltage Ejn outputs an output voltage VOI, which is the main output, between the terminal 4 and the terminal 6 (ground), and outputs an output voltage VO2, which is the sub-output, between the terminal 5 and the terminal 6. It is. It is assumed that the sequence is defined such that the output voltage VO2 rises after the output voltage V x rises, and the output voltage O1 falls after the fall of the output voltage VO2.

Furthermore, the error amplifier 7 is connected to the terminal 4 via voltage dividing resistors 8 to 10.
Regarding the output voltage VOt between one terminal 6, an error with respect to the reference voltage from the reference power supply 11 is detected, and feedback is applied to the power converter 3 by the output 16. In other words, by this feedback control, the output voltage between the terminals 4 and 6 is held constant.

Furthermore, in order to realize the above-described sequence, the voltage detector 14 monitors the output voltage VOI between the terminal 4 and the terminal 6 via the voltage dividing resistors 12 and 13.

When the output voltage v01 is higher than the reference voltage from the reference power supply 11, the output 17 is sent out from the voltage detector 14 and turns on the power supply circuit 15, and when it is lower, the output 17 is not sent out and the power supply circuit 15 is turned off. It is controlled so that As a result, the output voltage V old and the output voltage VO2
The sequence is defined accordingly.

Next, the operation of the power output circuit shown in FIG. 3 will be explained using the waveform diagram shown in FIG. 4. In the figure, the voltage that rises first (
The voltage detector 14 compares the output voltage of terminal 4) with the reference voltage Vs from the reference power supply 11, and when the output voltage of terminal 4 reaches the reference voltage, generates a voltage that rises with a delay (voltage of terminal 5). The power supply circuit 15 is driven. As a result, the output voltage at the terminal 5 rises later than the output voltage at the terminal 14 (■).

On the other hand, when the power is off, when the voltage at terminal 4 begins to drop and drops below the reference voltage of voltage detector 14, conversely, power supply circuit 15 is turned off, and the voltage at terminal 5 begins to drop (■
). If the time constant of the power supply circuit 15 is set so that the output voltage of the terminal 4 falls earlier than the output voltage of the terminal 4 at this fall, the output voltage of the terminal 5 will be lower than the output voltage of the terminal 4 at the rise. The sequence can be defined so that when the signal falls late, it falls early.

However, in the conventional power output circuit described above, since the output voltage of the terminal 4 is monitored and the above-mentioned control is performed, the rise of the output voltage of the terminal 5 occurs during the rise of the terminal 4.
The detection voltage of the voltage detector 14 must be accurately set so that the falling edge is during the falling edge, and this setting is difficult.

OBJECTS OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional drawbacks, and its purpose is to provide a power output circuit in which it is easy to set a reference voltage for defining a sequence.

Structure of the Invention A power supply output circuit according to the present invention includes: voltage sending means for sending out first and second output voltages; error voltage detecting means for detecting an error voltage of the first output voltage with respect to a reference voltage;
output voltage control means for controlling the first output voltage according to this error voltage; and voltage control means for turning off the second output voltage when the error voltage reaches a value outside a predetermined voltage range. It is characterized by having.

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

FIG. 1 is a circuit diagram showing the configuration of a power output circuit according to the present invention, and parts equivalent to those in FIG. 3 are designated by the same symbols.

In the figure, 1 and 2 are power input terminals, 4 and 5 are voltage output terminals, and 6 is a ground terminal. 3 is a power converter that stabilizes the output voltage, and 7 is an error amplifier that performs feedback control to stabilize the output voltage of the terminal 4. 11
1 is a reference power source, 8.9 and 10 are voltage dividing resistors, 14 is a voltage detector, and 15 is a power supply circuit for stabilizing the output voltage of the terminal 5.

In this embodiment, the power supply circuit 15 is configured to be controlled according to the output el of the error amplifier 7.

In this configuration, when the power is turned on, the output voltage VOI gradually rises as shown in FIG. 2, but the output of the error amplifier 7 remains saturated until it reaches the specified output voltage value. . Thereafter, when the output voltage vO1 reaches a specified voltage value, the output voltage of the error amplifier 7 suddenly becomes a certain voltage, and feedback control is performed to keep the output voltage V of the output terminal 4 constant. The voltage detector 14 detects this sudden change and operates the power supply circuit 15, whereby the output voltage VO2 of the terminal 5 rises with a delay (■).

That is, when the output el exceeds the reference voltage at the voltage detector 14, the output voltage VO2 rises.

On the other hand, when the power is turned off, the output voltage of the terminal 4 cannot be maintained constant even by feedback control, and when the output voltage exceeds the output stability range, the output of the error amplifier 7 also changes rapidly. When the voltage detector 14 detects this sudden change, the power supply circuit 15 is turned off and brought down (■
).

In other words, in this embodiment, the output voltage of the main output error amplifier 7 is detected, and when the voltage value is outside a predetermined voltage range, that is, when it changes rapidly, the output voltage of the sub output is turned on/off. By doing this, the sequence of the main output voltage and the sub-output voltage is accurately maintained. Furthermore, in this case, the output voltage of the error amplifier 7, that is, the amplified result, can be detected by the voltage detector 14, so there is no need to precisely set the reference voltage of the voltage detector 14, and the setting is easy. It will become.

DETAILED DESCRIPTION OF THE INVENTION As described in the detailed description of the invention, the present invention changes the sequence between the main output and the sub output by turning the sub output on and off in response to a sudden change in the error amplification output used for the main output fitback control. This has the effect that the specified reference voltage can be easily set.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a power output circuit according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the operation of FIG. 1, and FIG. 3 is a circuit diagram showing the configuration of a conventional power output circuit. FIG. 4 is a waveform diagram showing the operation of FIG. 3. Explanation of symbols of main parts 3... Power converter 7... Error amplifier 11... Reference power supply 14... Voltage detector 15...・Power supply circuit diagram 1

Claims (1)

[Claims] (1) Voltage sending means for sending out first and second output voltages; error voltage detection means for detecting an error voltage of the first output voltage with respect to a reference voltage; A power supply output circuit comprising: an output voltage control means for controlling an output voltage; and a voltage control means for turning off the second output voltage when the error voltage becomes a value outside a predetermined voltage range.