CN109194109B

CN109194109B - Compensation circuit

Info

Publication number: CN109194109B
Application number: CN201811130689.4A
Authority: CN
Inventors: 林泽钦; 周雨发; 冯刚
Original assignee: Mornsun Guangzhou Science and Technology Ltd
Current assignee: Mornsun Guangzhou Science and Technology Ltd
Priority date: 2018-09-27
Filing date: 2018-09-27
Publication date: 2024-07-19
Anticipated expiration: 2038-09-27
Also published as: CN109194109A

Abstract

The invention provides a compensation circuit scheme. The relative high voltage of the power port VDD of the control IC when the specific load jumps is used as a control signal to control the compensation loop to compensate the soft start unit, so that the successful soft start when the specific load jumps is ensured, the false triggering of the control IC to the protection state is avoided, and the stable output is maintained. The invention has simple circuit and low realization cost, and creatively avoids the problem of abnormal output when the power module carries capacitive load to switch load under low-voltage input. Meanwhile, compensation is carried out when the control signal and the compensation power supply exist simultaneously, and the normal steady-state operation of the system is not influenced.

Description

Compensation circuit

Technical Field

The present invention relates to a compensation circuit, and more particularly, to a compensation circuit for compensating a feedback pin of a control IC in a switching power supply.

Background

In the switching power supply, as shown in fig. 1, a conventional peripheral circuit of a control IC part is shown, wherein IC1 is a control IC, the peripheral circuit of IC1 is composed of an isolated feedback optocoupler OC1, a resistor R1, a capacitor C1, a power supply winding L1, a diode D1, a capacitor C2, and a capacitor C3, and the control IC pins are as follows:

VIN: an input voltage detection pin can be provided with UVP protection (under voltage protection, chinese name: under-voltage protection) and feedforward compensation;

VDD: a power port for inputting a control IC power supply voltage;

And (B): the voltage feedback pin is used for feeding back an output voltage signal;

GATE: the switching tube drives the output port;

CS: a current sampling input port;

GND: the control IC is referenced to ground;

BOS: the BOOST pin and the peripheral circuit form a BOOST circuit, and the output square wave signal controls the BOOST circuit to BOOST the input voltage, so that the power port VDD of the IC1 can reach an opening value under low voltage;

RI: the frequency setting pin is externally connected with a resistor to the ground to set the working frequency.

In the prior art, a control IC feedback pin FB is generally configured to slowly rise during a startup process to improve startup overshoot, i.e., soft start, when the feedback pin FB participates in controlling the soft start, the feedback pin FB is an external pin of the control IC soft start unit. During the start-up process, if the level of the feedback pin FB fails to rise normally within a certain period (hereinafter referred to as a timer period), the soft start fails, and at this time, the control IC usually considers that the operation is abnormal and enters a protection state. When the load with the capacitive load is output, if the load jumps from heavy load to light load, the output voltage is maintained above a set value for a long time, so that the control IC feedback pin FB is electrified to low level, and the driving of the switching tube is stopped. In the switching power supply, since the power supply to the control IC is generally supplied by a transformer winding, the power supply port VDD of the control IC is not supplied during the period when the driving of the switching transistor is stopped, and is maintained only by the energy storage capacitor. When the input voltage is lower than the under-voltage protection value of the control IC power supply port VDD, the voltage of the control IC power supply port VDD can be reduced to the under-voltage protection value, the circuit is designed to control the IC to restart, at the moment, soft start is needed again, the feedback pin FB of the control IC is still output to be powered up, the timing period cannot be increased normally, the soft start fails, the IC enters a protection state, and the output is abnormal.

For the above situation, the mode of increasing the energy storage capacitor of the power supply port VDD or the voltage of the power supply winding of the control IC can be generally adopted to avoid that the control IC is in soft start again due to the undervoltage of the power supply port VDD. The biggest shortcoming of this kind of mode is that even though the system has faster response speed, the time that the output is continuous to draw power IC feedback pin FB still is very long, and IC power port VDD energy storage capacitance theoretical calculation value reaches 10uF level, and this is unfavorable to miniaturization and the low cost of product. Meanwhile, a large energy storage capacitor also brings longer startup delay time.

Disclosure of Invention

In view of this, the present invention provides a compensation circuit that can compensate the feedback pin FB of the control IC during the timing period of restarting the control IC after the undervoltage protection of the power port of the control IC, so that the control IC can be normally and softly started, and the control IC is prevented from entering the protection state by mistake.

The invention is realized by the following technical scheme:

A compensation circuit for providing compensation for a feedback pin FB of a control IC, characterized by: comprises a signal detection unit and a compensation loop unit; the signal detection unit is used for detecting the voltage of the power port VDD of the control IC, when the voltage is higher than a set value, the signal detection unit outputs a control signal to the control end of the compensation loop unit, the compensation loop unit is controlled to start working, at the moment, the input end of the compensation loop unit inputs the compensation signal, the output end of the compensation loop unit is connected with the feedback pin FB of the control IC, and the output compensation signal pulls up the level of the feedback pin FB of the control IC.

Preferably, the input terminal of the compensation loop unit is connected to the power supply port VDD, and the voltage of the power supply port VDD is used as the compensation signal.

As a first specific embodiment of the signal detection unit and the compensation loop unit, the signal detection unit is a zener diode D1, the compensation loop unit includes a zener diode D1 and a current limiting resistor R1, an anode of the zener diode D1 is used for being connected to a feedback pin FB of the control IC, a cathode of the zener diode D1 is connected to one end of the current limiting resistor R1, and the other end of the current limiting resistor R1 is used for being connected to a power port VDD of the control IC.

As an equivalent replacement of the first specific embodiment of the signal detection unit and the compensation loop unit, the signal detection unit is a zener diode D1, the compensation loop unit includes a zener diode D1 and a current limiting resistor R1, a cathode of the zener diode D1 is used for being connected to a power port VDD of the control IC, an anode of the zener diode D1 is connected to one end of the current limiting resistor R1, and the other end of the current limiting resistor R1 is used for being connected to a feedback pin FB of the control IC.

As a second specific embodiment of the signal detection unit and the compensation circuit unit, the signal detection unit includes voltage dividing resistors R1 and R2, and the compensation circuit unit includes a current limiting resistor R3, an NPN triode Q1 and a regulator tube D1; one end of each of the voltage dividing resistors R1 and R2 is connected in series and then is used for being connected with a power port VDD of the control IC, the other end of each of the voltage dividing resistors is used for being connected to the ground, and a connection point of each of the voltage dividing resistors R1 and R2 is connected with a control end of the compensation loop unit; one end of the current limiting resistor R3 is an input end of the compensation loop unit, the other end of the current limiting resistor R3 is connected with a collector electrode of the NPN triode Q1, a base level of the NPN triode Q1 is a control end of the compensation loop unit, an emitter electrode of the NPN triode Q1 is an output end of the compensation loop unit, a cathode electrode of the voltage stabilizing tube D1 is connected with an emitter electrode of the NPN triode Q1, and an anode electrode of the voltage stabilizing tube D1 is connected to the ground.

As an equivalent replacement of the second specific embodiment of the signal detection unit and the compensation circuit unit, the signal detection unit includes voltage dividing resistors R1 and R2, and the compensation circuit unit includes a current limiting resistor R3, an NPN triode Q1 and a voltage regulator tube D1; one end of each of the voltage dividing resistors R1 and R2 is connected in series and then is used for being connected with a power port VDD of the control IC, the other end of each of the voltage dividing resistors is used for being connected to the ground, and a connection point of each of the voltage dividing resistors R1 and R2 is connected with a control end of the compensation loop unit; the collector of the NPN triode Q1 is an input end of the compensation loop unit, the base of the NPN triode Q1 is a control end of the compensation loop unit, the emitter of the NPN triode Q1 is connected with one end of a current limiting resistor R3, the other end of the current limiting resistor R3 is an output end of the compensation loop unit, the cathode of the voltage stabilizing tube D1 is connected with the output end of the compensation loop unit, and the anode of the voltage stabilizing tube D1 is connected to the ground.

As a third specific embodiment of the signal detection unit and the compensation circuit unit, the signal detection unit includes voltage dividing resistors R1 and R2 and a three-terminal voltage regulator IC2, and the compensation circuit unit is a PNP triode Q1; one end of the divider resistor R1 and the divider resistor R2 are connected in series, the other end of the divider resistor R1 and the divider resistor R2 are connected with a power port VDD of the control IC, the other end of the divider resistor R2 is connected with the ground, a reference pin of the three-terminal voltage regulator IC2 is connected with a connection point of the divider resistor R1 and the divider resistor R2, an anode of the three-terminal voltage regulator IC2 is connected with the ground, and a cathode of the three-terminal voltage regulator IC2 is connected with a control end of the compensation loop unit; the emitter of the PNP triode Q1 is the input end of the compensation loop unit, the base electrode of the PNP triode Q1 is the control end of the compensation loop unit, and the collector electrode of the PNP triode Q1 is the output end of the compensation loop unit.

As a preferred mode of the third specific embodiment of the compensation loop unit, the input terminal of the compensation loop unit is also used for connection to the control IC power supply port VDD.

As a fourth specific embodiment of the signal detection unit and the compensation circuit unit, the signal detection unit includes voltage dividing resistors R1 and R2, a three-terminal voltage regulator IC2 and a PNP triode Q1, and the compensation circuit unit is an NPN triode Q2; one end of the voltage dividing resistor R1 and the resistor R2 are connected in series and then are used for being connected with a control IC power port VDD, the other end of the voltage dividing resistor R1 and the resistor R2 are connected to the ground, a reference pin of the three-terminal voltage regulator IC2 is connected with a connection point of the voltage dividing resistor R1 and the resistor R2, an anode of the three-terminal voltage regulator IC2 is connected to the ground, a cathode of the three-terminal voltage regulator IC2 is connected with a base electrode of the PNP triode Q1, an emitter of the PNP triode Q1 is also used for being connected with the control IC power port VDD, and a collector of the PNP triode Q1 is connected with a control end of the compensation loop unit; the collector of the PNP triode Q2 is the input end of the compensation loop unit, the base of the PNP triode Q2 is the control end of the compensation loop unit, and the emitter of the PNP triode Q2 is the output end of the compensation loop unit.

As a fifth specific embodiment of the signal detection unit and the compensation circuit unit, the signal detection unit includes voltage dividing resistors R1 and R2, a three-terminal voltage regulator IC2 and an NPN triode Q1, and the compensation circuit unit is a PNP triode Q2; one end of the voltage dividing resistor R1 and the resistor R2 are connected in series and then are used for being connected with a control IC power port VDD, the other end of the voltage dividing resistor R1 and the resistor R2 are connected to the ground, a reference pin of the three-terminal voltage regulator IC2 is connected with a connection point of the voltage dividing resistor R1 and the resistor R2, an anode of the three-terminal voltage regulator IC2 is connected to the ground, a cathode of the three-terminal voltage regulator IC2 is connected with an emitter of the PNP triode Q1, a base electrode of the PNP triode Q1 is also used for being connected with the control IC power port VDD, and a collector electrode of the PNP triode Q1 is connected with a control end of the compensation loop unit; the emitter of the PNP triode Q2 is the input end of the compensation loop unit, the base electrode of the PNP triode Q2 is the control end of the compensation loop unit, and the collector of the PNP triode Q2 is the output end of the compensation loop unit.

The working principle of the invention is as follows: under the condition of the output load, if the load jumps from heavy load to light load, the output voltage is maintained above a set value for a long time, so that the control IC feedback pin FB is electrified to low level, and the driving of the switching tube is stopped. In the switching power supply, since the power supply to the control IC is generally supplied by a transformer winding, the power supply port VDD of the control IC is not supplied during the period when the driving of the switching transistor is stopped, and is maintained only by the energy storage capacitor. When the input voltage is a low voltage less than the under-voltage protection value of the control IC power supply port VDD, the control IC power supply port VDD voltage will drop to the under-voltage protection value. At this time, the circuit is designed as a control IC restarting machine, the BOOST pin BOS of the control IC outputs a square wave signal to control the BOOST circuit inside the IC to BOOST the input voltage, so that the power port VDD of the control IC reaches the on value again, and then the control IC performs soft start again. Meanwhile, the control IC enters a timing period, and the BOS pin of the control IC outputs square waves to maintain the voltage of the power port VDD of the control IC during the timing period, so that the repeated undervoltage of the power port VDD of the control IC is avoided, and the power port VDD of the control IC is maintained below the VDD starting value by low voltage return difference. If the circuit of the invention is not provided, the feedback pin FB of the control IC is output to feed back and draw power during soft start, the soft start fails, and the IC enters a protection state. The invention establishes the compensation channel for the feedback pin FB of the control IC by detecting the high voltage of the power port VDD of the control IC, feeds the feedback pin FB of the control IC in the process of restarting the soft start, so that the soft start is successfully completed, the VDD voltage is recovered to a steady-state working voltage range after the system is normally transited to a light load state in a timing period, and the power supply is insufficient to control the compensation circuit to work, thus stopping the feed of the feedback pin FB of the control IC and not participating in the regulation of feedback signals.

The invention uses the voltage under the special condition of the system pin as the control to compensate, and has the following remarkable characteristics:

1. the invention effectively avoids the false triggering protection state of the control IC under the load disturbance, and the system output is normal;

2. the invention only compensates under the special high voltage of VDD, and has no influence on the system when the system works stably;

3. the invention uses the self power supply of the system to compensate, thereby greatly saving peripheral circuits, and the circuit scheme is simple and easy to realize.

Drawings

FIG. 1 is a schematic diagram of a conventional peripheral circuit of a control IC;

FIG. 2 is a functional implementation block diagram of the present invention;

FIG. 3 is a first embodiment of the present invention;

FIG. 4 is a second embodiment of the present invention;

FIG. 5 is a third embodiment of the present invention;

FIG. 6 is a fourth embodiment of the present invention;

fig. 7 is a fifth embodiment of the present invention.

Detailed Description

FIG. 2 is a functional block diagram of an implementation of the present invention, the circuit block diagram including a signal detection unit and a compensation loop unit; the input end of the signal detection unit is used for being connected with a power port VDD of the control IC, the output end of the signal detection unit is connected with the control end of the compensation loop unit, the input end of the compensation loop unit is used for being connected with a compensation source, and the output end of the compensation loop unit is used for being connected with a feedback pin FB of the control IC.

Fig. 2 is a functional implementation block diagram of the standard of the present invention, and after the signal detection unit and the compensation loop unit adopt different implementation circuits, the multiplexing of components and the serial circuit switching positions do not affect the functions, which will cause the connection mode of the functional implementation block diagram to change, and this situation can be seen from the detailed description, and is not drawn one by one here.

The application is characterized in that the relative high voltage of the power supply port VDD of the control IC when a specific load jumps is used as a control signal, the compensation loop is controlled to compensate the soft start unit, the successful execution of soft start when the specific load jumps is ensured, the false triggering of the protection state of the control IC is avoided, the output stability is maintained, the problem of abnormal output when the power supply module carries out load switching with capacitive load under low voltage input is avoided, meanwhile, the compensation is carried out only when the control signal and the compensation power supply exist simultaneously (such as the timing period mentioned above), and the normal steady-state operation of the system is not influenced.

In order that those skilled in the art will better understand the present application, a specific embodiment will be described below.

First embodiment

Fig. 3 shows a first embodiment of the application of the invention.

The signal detection unit in this embodiment is a zener diode D1, the compensation loop unit includes a zener diode D1 and a current limiting resistor R1, an anode of the zener diode D1 is connected to a feedback pin FB of the control IC, a cathode of the zener diode D1 is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to a power port VDD of the control IC.

The cathode of the zener diode D1 in this embodiment is an input end of the signal detection unit, and the anode of the zener diode D1 is an output end of the signal detection unit; the voltage stabilizing diode D1 is multiplexed in the signal detection unit and the compensation loop unit, the other end of the resistor R1 is an input end of the compensation loop unit, the cathode of the voltage stabilizing diode D1 is a control end of the compensation loop unit, and the anode of the voltage stabilizing diode D1 is an output end of the compensation loop unit; the compensation source input at the input end of the compensation loop unit is the voltage of the power supply port VDD of the control IC.

The working principle of this embodiment is the same as the analysis of the summary section, and only the working principle of the signal detection unit and the compensation loop unit circuit is described here as follows:

When the voltage of the power port VDD of the control IC is boosted by the control BOOST circuit, the voltage at two ends of the voltage stabilizing diode D1 reaches the reverse breakdown voltage to start to stabilize the voltage, meanwhile, the power port VDD of the control IC compensates the feedback pin FB of the control IC through the current limiting resistor R1 and the voltage stabilizing diode D1, and the magnitude of the compensation current can be regulated through the current limiting resistor R1. This compensation promotes successful soft start and the system transitions to light load. At this time, the control IC exits the timing cycle, the BOS pin stops outputting the square wave signal, the VDD voltage drops below the reverse breakdown voltage of the regulator D1, and the compensation stops.

The embodiment has the following 4 beneficial effects:

1. The circuit is simple, and the device cost is low;

2. The voltage for controlling the compensation loop unit to start working can be accurately designed according to the characteristics of the voltage stabilizing tube;

3. The specific working state of the specific pin is compensated, so that the normal operation of the system is not negatively influenced;

4. the power supply end of the compensation loop unit selects a port VDD with strong power supply capacity, and has larger compensation capacity.

It should be noted that, in this embodiment, the control IC power port VDD is taken as a control signal, and the design of the VDD voltage in the steady state needs to avoid the control signal voltage when the compensation circuit works.

In addition, the zener diode D1 and the current limiting resistor R1 in this embodiment are connected in series, and the two can exchange positions, which can also achieve the purpose of the invention.

Second embodiment

Fig. 4 shows a second embodiment of the application of the invention.

The signal detection unit in the present embodiment includes voltage dividing resistors R1 and R2; the compensation loop unit comprises a current limiting resistor R3, an NPN triode Q1 and a voltage stabilizing tube D1; one end of the current limiting resistor R3 is connected with the compensation source SFB, the other end of the current limiting resistor R3 is connected with the collector electrode of the NPN triode Q1, the base level of the NPN triode Q1 is connected with the connection point of the voltage dividing resistors R1 and R2, the emitter electrode of the NPN triode Q1 is connected with the feedback pin FB of the control IC, the cathode of the voltage stabilizing tube D1 is connected with the feedback pin FB of the control IC, the anode is connected to the ground, one end of the voltage dividing resistor R1 is connected with the power supply port VDD, the other end of the voltage dividing resistor R1 is connected with the base level of the NPN triode Q1, one end of the voltage dividing resistor R2 is connected to the ground, and the other end of the voltage dividing resistor R1 is connected with the base level of the NPN triode Q1.

One end of the voltage dividing resistor R1 is an input end of the signal detection unit, the other end of the voltage dividing resistor R1 and one end of the voltage dividing resistor R2 are output ends of the signal detection unit, one end of the current limiting resistor R3 is an input end of the compensation loop unit, a base electrode of the NPN triode Q1 is a control end of the compensation loop unit, and an emitter electrode of the NPN triode Q1 is an output end of the compensation loop unit.

The base voltage of the NPN triode Q1 is divided by the voltage dividing resistors R1 and R2 to the power port VDD of the control IC, when the voltage of the power port VDD is boosted by the control BOOST circuit, the transmitting junction of the NPN triode Q1 is conducted to reach the conducting voltage, at the moment, the compensation source SFB provides FB compensation for the feedback pin of the control IC through the NPN triode Q1, the size of compensation current can be adjusted by adjusting the parameter of the current limiting resistor R3, the voltage stabilizing tube D1 reversely breaks down and shunts when the voltage of the feedback pin FB of the control IC rises at a set value in the compensation process, and the voltage limiting effect is achieved. This compensation promotes successful soft start and the system transitions to light load. At this time, the control IC exits the timing cycle, the BOS pin stops outputting square wave signals, and the VDD voltage drops, so that the NPN transistor Q1 is turned off and compensation stops.

This embodiment also has 4 beneficial effects of the first embodiment, and is not described here again.

In addition, the triode Q1 and the current limiting resistor R3 can be switched in position, and the aim of the invention can be achieved.

Third embodiment

Fig. 5 shows a third embodiment of the application of the invention.

The signal detection unit in the present embodiment includes voltage dividing resistors R1, R2 and a three-terminal voltage regulator IC2; the compensation loop unit is a PNP triode Q1; the emitter of PNP triode Q1 connects power supply port VDD, the collector of PNP triode Q1 connects control IC's feedback pin FB, PNP triode Q1's base is connected three terminal regulator IC 2's negative pole, three terminal regulator IC 2's positive pole is connected to ground, three terminal regulator IC 2's reference foot connects divider resistance R1 and R2's one end, divider resistance R1 other end is connected to power supply port VDD, the divider resistance R2 other end is connected to three terminal regulator IC 2's positive pole.

The other end of the divider resistor R1 is an input end of the signal detection unit, the cathode of the three-terminal voltage regulator IC2 is an output end of the signal detection unit, the emitter of the PNP triode Q1 is an input end of the compensation loop unit, the base of the NPN triode Q1 is a control end of the compensation loop unit, and the collector of the PNP triode Q1 is an output end of the compensation loop unit.

The reference pin voltage of the three-terminal voltage regulator IC2 is divided by the voltage dividing resistors R1 and R2 to divide the power supply port VDD, when the voltage of the power supply port VDD is boosted by the control BOOST circuit, the reference pin voltage of the IC2 is raised and higher than the internal reference voltage of the IC2, current starts to flow into the reference pin of the IC2, the PNP triode Q1 starts to be conducted at the moment, compensation is provided for the feedback pin FB of the control IC through the power supply port VDD, and the magnitude of the compensation current can be adjusted by adjusting parameters of the voltage dividing resistors R1 and R2. This compensation promotes successful soft start and the system transitions to light load. At this time, the control IC exits the timing period, the BOS pin stops outputting the square wave signal, the VDD voltage decreases, the reference pin voltage of the three-terminal regulator IC2 decreases, and when the reference voltage is lower than the internal reference voltage of the IC2, the current stops flowing into the cathode of the three-terminal regulator IC2, and the PNP transistor Q1 is turned off, stopping compensation.

It should be noted that, in this embodiment, the control IC power port VDD is taken as the control signal, and the design of the VDD voltage in the steady state needs to avoid the control signal voltage when the compensation circuit works.

Fourth embodiment

Fig. 6 shows a fourth embodiment of the application of the invention.

The signal detection unit in the embodiment comprises divider resistors R1 and R2, a three-terminal voltage regulator IC2 and a PNP triode Q1; the compensation loop unit is an NPN triode Q2; the emitter of the PNP triode Q1 is connected with the power supply port VDD, the collector of the PNP triode Q1 is connected with the base of the NPN triode Q2, and the base of the PNP triode Q1 is connected with the cathode of the three-terminal voltage regulator IC 2; the emitter of the NPN triode Q2 is connected with a feedback pin FB of the control IC, and the collector of the NPN triode Q2 is connected with a compensation source SFB; the anode of the three-terminal voltage regulator IC2 is connected to the ground, the reference pin of the three-terminal voltage regulator IC2 is connected with one ends of the voltage dividing resistors R1 and R2, the other end of the voltage dividing resistor R1 is connected to the power supply port VDD, and the other end of the voltage dividing resistor R2 is connected to the anode of the IC 2.

The other end of the divider resistor R1 is an input end of the signal detection unit, a collector electrode of the PNP triode Q1 is an output end of the signal detection unit, an emitter electrode of the PNP triode Q1 is an input end of the compensation loop unit, a base electrode of the NPN triode Q2 is a control end of the compensation loop unit, and an emitter electrode of the NPN triode Q2 is an output end of the compensation loop unit.

The reference pin voltage of the three-terminal voltage regulator IC2 is divided by the voltage dividing resistors R1 and R2 to divide the power supply port VDD, when the voltage of the power supply port VDD is boosted by the control BOOST circuit, the reference pin voltage of the three-terminal voltage regulator IC2 is raised, when the reference pin voltage is higher than the internal reference voltage of the three-terminal voltage regulator IC2, current starts to flow into the cathode of the three-terminal voltage regulator IC2, the PNP triode Q1 starts to be conducted at the moment, the NPN triode Q2 also starts to be conducted, further, the compensation source SFB provides FB compensation for the feedback pin of the control IC, and the magnitude of compensation current can be adjusted by adjusting parameters of the voltage dividing resistors R1 and R2. This compensation promotes successful soft start and the system transitions to light load. At this time, the control IC exits the timing period, the BOS pin stops outputting the square wave signal, the VDD voltage decreases, the reference pin voltage of the three-terminal regulator IC2 decreases, and when the reference voltage is lower than the internal reference voltage of the three-terminal regulator IC2, the current stops flowing into the cathode of the three-terminal regulator IC2, and the PNP transistor Q1 and NPN transistor Q2 are turned off, stopping compensation.

Fifth embodiment

Fig. 7 shows a fifth embodiment of the application of the invention.

The signal detection unit in the embodiment comprises divider resistors R1 and R2, a three-terminal voltage regulator IC2 and an NPN triode Q1; the compensation loop unit is a PNP triode Q2; an emitter of the NPN triode Q1 is connected with a cathode of the three-terminal voltage regulator IC2, a collector of the NPN triode Q1 is connected with a base of the PNP triode Q2, and a base of the NPN triode Q1 is connected with a power supply port VDD; the emitter of the PNP triode Q2 is connected with the compensation source SFB, and the collector of the PNP triode Q2 is connected with the feedback pin FB of the control IC; the anode of the three-terminal voltage regulator IC2 is connected to the ground, the reference pin of the three-terminal voltage regulator IC2 is connected with one ends of the voltage dividing resistors R1 and R2, the other end of the voltage dividing resistor R1 is connected to the power supply port VDD, and the other end of the voltage dividing resistor R2 is connected to the anode of the three-terminal voltage regulator IC 2.

The other end of the divider resistor R1 is an input end of the signal detection unit, a collector electrode of the NPN triode Q1 is an output end of the signal detection unit, a base electrode of the NPN triode Q2 is a control end of the compensation loop unit, an emitter electrode of the NPN triode Q2 is an input end of the compensation loop unit, and a collector electrode of the NPN triode Q2 is an output end of the compensation loop unit.

The reference pin voltage of the three-terminal voltage regulator IC2 is divided by the voltage dividing resistors R1 and R2 to divide the power supply port VDD, when the voltage of the power supply port VDD is boosted by controlling the BOOST circuit, the reference pin voltage of the three-terminal voltage regulator IC2 is raised, when the reference pin voltage is higher than the internal reference voltage of the three-terminal voltage regulator IC2, current starts to flow into the cathode of the three-terminal voltage regulator IC2, at the moment, the NPN triode Q1 starts to be conducted, the PNP triode Q2 starts to be conducted, and further, the feedback pin of the control IC is provided with FB compensation by the compensation source SFB, and the magnitude of the compensation current can be adjusted by adjusting parameters of the voltage dividing resistors R1 and R2. This compensation promotes successful soft start and the system transitions to light load. At this time, the control IC exits the timing period, the BOS pin stops outputting square wave signals, the VDD voltage drops, the reference pin voltage of the three-terminal regulator IC2 will drop, and when the reference voltage is lower than the internal reference voltage of the three-terminal regulator IC2, the current stops flowing into the cathode of the three-terminal regulator IC2, so that the NPN transistor Q1 and the PNP transistor Q2 are turned off, and the compensation is stopped.

It should be noted that the above-mentioned preferred embodiments should not be regarded as limiting the invention, and that it will be apparent to those skilled in the art that several modifications and adaptations can be made without departing from the spirit and scope of the invention, and that these modifications and adaptations should and are intended to be comprehended within the scope of the invention as set forth in the following claims.

Claims

1.A compensation circuit for providing compensation for a feedback pin FB of a control IC, characterized by: comprises a signal detection unit and a compensation loop unit; the signal detection unit is used for detecting the voltage of the power port VDD of the control IC, when the voltage is higher than a set value, the signal detection unit outputs a control signal to the control end of the compensation loop unit, the compensation loop unit is controlled to start working, at the moment, the input end of the compensation loop unit inputs the compensation signal, the output end of the compensation loop unit is connected with the feedback pin FB of the control IC, and the output compensation signal pulls up the level of the feedback pin FB of the control IC.

2. The compensation circuit of claim 1, wherein: the input end of the compensation loop unit is connected with the power supply port VDD, and the voltage of the power supply port VDD is used as a compensation signal.

3. The compensation circuit of claim 1, wherein: the signal detection unit is a voltage-stabilizing diode D1, the compensation loop unit comprises the voltage-stabilizing diode D1 and a current-limiting resistor R1, the anode of the voltage-stabilizing diode D1 is used for being connected with a feedback pin FB of the control IC, the cathode of the voltage-stabilizing diode D1 is connected with one end of the current-limiting resistor R1, and the other end of the current-limiting resistor R1 is used for being connected with a power port VDD of the control IC.

4. The compensation circuit of claim 1, wherein: the signal detection unit is a voltage-stabilizing diode D1, the compensation loop unit comprises the voltage-stabilizing diode D1 and a current-limiting resistor R1, the cathode of the voltage-stabilizing diode D1 is used for being connected with a power port VDD of the control IC, the anode of the voltage-stabilizing diode D1 is connected with one end of the current-limiting resistor R1, and the other end of the current-limiting resistor R1 is used for being connected with a feedback pin FB of the control IC.

5. The compensation circuit of claim 1, wherein: the signal detection unit comprises divider resistors R1 and R2, and the compensation loop unit comprises a current limiting resistor R3, an NPN triode Q1 and a voltage stabilizing tube D1; one end of each of the voltage dividing resistors R1 and R2 is connected in series and then is used for being connected with a power port VDD of the control IC, the other end of each of the voltage dividing resistors is used for being connected to the ground, and a connection point of each of the voltage dividing resistors R1 and R2 is connected with a control end of the compensation loop unit; one end of the current limiting resistor R3 is an input end of the compensation loop unit, the other end of the current limiting resistor R3 is connected with a collector electrode of the NPN triode Q1, a base level of the NPN triode Q1 is a control end of the compensation loop unit, an emitter electrode of the NPN triode Q1 is an output end of the compensation loop unit, a cathode electrode of the voltage stabilizing tube D1 is connected with an emitter electrode of the NPN triode Q1, and an anode electrode of the voltage stabilizing tube D1 is connected to the ground.

6. The compensation circuit of claim 1, wherein: the signal detection unit comprises divider resistors R1 and R2, and the compensation loop unit comprises a current limiting resistor R3, an NPN triode Q1 and a voltage stabilizing tube D1; one end of each of the voltage dividing resistors R1 and R2 is connected in series and then is used for being connected with a power port VDD of the control IC, the other end of each of the voltage dividing resistors is used for being connected to the ground, and a connection point of each of the voltage dividing resistors R1 and R2 is connected with a control end of the compensation loop unit; the collector of the NPN triode Q1 is an input end of the compensation loop unit, the base of the NPN triode Q1 is a control end of the compensation loop unit, the emitter of the NPN triode Q1 is connected with one end of a current limiting resistor R3, the other end of the current limiting resistor R3 is an output end of the compensation loop unit, the cathode of the voltage stabilizing tube D1 is connected with the output end of the compensation loop unit, and the anode of the voltage stabilizing tube D1 is connected to the ground.

7. The compensation circuit of claim 1, wherein: the signal detection unit comprises divider resistors R1 and R2 and a three-terminal voltage regulator IC2, and the compensation loop unit is a PNP triode Q1; one end of the divider resistor R1 and the divider resistor R2 are connected in series, the other end of the divider resistor R1 and the divider resistor R2 are connected with a power port VDD of the control IC, the other end of the divider resistor R2 is connected with the ground, a reference pin of the three-terminal voltage regulator IC2 is connected with a connection point of the divider resistor R1 and the divider resistor R2, an anode of the three-terminal voltage regulator IC2 is connected with the ground, and a cathode of the three-terminal voltage regulator IC2 is connected with a control end of the compensation loop unit; the emitter of the PNP triode Q1 is the input end of the compensation loop unit, the base electrode of the PNP triode Q1 is the control end of the compensation loop unit, and the collector electrode of the PNP triode Q1 is the output end of the compensation loop unit.

8. The compensation circuit of claim 7, wherein: the input of the compensation loop unit is also used for connecting to the control IC power supply port VDD.

9. The compensation circuit of claim 1, wherein: the signal detection unit comprises divider resistors R1 and R2, a three-terminal voltage regulator IC2 and a PNP triode Q1, and the compensation loop unit is an NPN triode Q2; one end of the voltage dividing resistor R1 and the resistor R2 are connected in series and then are used for being connected with a control IC power port VDD, the other end of the voltage dividing resistor R1 and the resistor R2 are connected to the ground, a reference pin of the three-terminal voltage regulator IC2 is connected with a connection point of the voltage dividing resistor R1 and the resistor R2, an anode of the three-terminal voltage regulator IC2 is connected to the ground, a cathode of the three-terminal voltage regulator IC2 is connected with a base electrode of the PNP triode Q1, an emitter of the PNP triode Q1 is also used for being connected with the control IC power port VDD, and a collector of the PNP triode Q1 is connected with a control end of the compensation loop unit; the collector of the PNP triode Q2 is the input end of the compensation loop unit, the base of the PNP triode Q2 is the control end of the compensation loop unit, and the emitter of the PNP triode Q2 is the output end of the compensation loop unit.

10. The compensation circuit of claim 1, wherein: the signal detection unit comprises divider resistors R1 and R2, a three-terminal voltage regulator IC2 and an NPN triode Q1, and the compensation loop unit is a PNP triode Q2; one end of the voltage dividing resistor R1 and the resistor R2 are connected in series and then are used for being connected with a control IC power port VDD, the other end of the voltage dividing resistor R1 and the resistor R2 are connected to the ground, a reference pin of the three-terminal voltage regulator IC2 is connected with a connection point of the voltage dividing resistor R1 and the resistor R2, an anode of the three-terminal voltage regulator IC2 is connected to the ground, a cathode of the three-terminal voltage regulator IC2 is connected with an emitter of the PNP triode Q1, a base electrode of the PNP triode Q1 is also used for being connected with the control IC power port VDD, and a collector electrode of the PNP triode Q1 is connected with a control end of the compensation loop unit; the emitter of the PNP triode Q2 is the input end of the compensation loop unit, the base electrode of the PNP triode Q2 is the control end of the compensation loop unit, and the collector of the PNP triode Q2 is the output end of the compensation loop unit.