A main power conversion detection circuit for a power supply IC that can be turned off for a power module

Abstract

The present invention discloses a main-standby power conversion detection circuit for a power IC that can be turned off for a power module, which includes: an input voltage module, a reference voltage module, a comparator, an optical coupling module and a power IC control module; the input voltage module is connected to the AC input end of the power module, and is used to filter and divide the voltage at the AC input end; the comparator compares the output voltages of the input voltage module and the reference voltage module, and disconnects the optical coupling module when the output voltage of the input voltage module is too low, and controls the power IC to be turned off through the power IC control module. The main-standby power conversion detection circuit of the present invention can continuously detect the input voltage of the AC input end, and automatically turn off the power IC when the input voltage is undervoltage, and turn on the power IC when the input voltage is normal, thereby realizing undervoltage protection for the power IC, and avoiding the problem of heating or even burning caused by long-term operation under low voltage.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a main-standby power conversion detection circuit for a power supply IC capable of being turned off and used in a power supply module. Background Art

[0002] In fire lamps, communication equipment or some medical equipment, the main power (AC mains) and backup power (battery) are usually used to back up each other to improve the reliability of the equipment and avoid equipment failure in the event of a power outage. The above equipment usually has a main-backup power conversion device for switching to the backup power supply when the main power fails.

[0003] The existing detection circuit usually includes sampling circuits, relays, single-chip microcomputers and other components. The existing main and backup power switching circuit usually only switches the line during the switching process, and does not control the main power and backup power. This method has a simple structure and low cost, but the reliability is insufficient under special circumstances.

[0004] For example, when the voltage of the main power supply is too low and the device switches to the backup power supply, if the power supply IC of the main power supply is not turned off, the power supply IC will continue to work. In this case, due to the low input voltage, the conduction period of the power supply IC will be extended, which will cause the power supply IC to heat up seriously when working at a low input voltage, and even burn the power supply, causing safety hazards. Summary of the invention

[0005] The purpose of the present invention is to provide a main-backup power conversion detection circuit for a power supply IC that can be shut down for a power module based on the above-mentioned deficiencies of the prior art. The circuit prompts the control module to switch to backup power and shuts down the power IC at the same time when it detects that the input voltage of the power module is too low, so as to solve the problems existing in the prior art.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A main-standby power conversion detection circuit for a power supply IC that can be turned off in a power supply module, the power supply module includes a power supply IC for chopping, the power supply IC has an enable terminal, and the main-standby power conversion detection circuit includes:

[0008] An input voltage module, connected to the AC input terminal of the power module, used to convert the input voltage of the power module into pulse direct current, and output the pulse direct current after voltage division;

[0009] A reference voltage module, used for generating a reference voltage;

[0010] A comparator, whose non-inverting end is connected to the output end of the reference voltage module, and whose inverting end is connected to the output end of the input voltage module; the output end of the comparator is connected to the VCC end through two pull-up resistors connected in series;

[0011] An optocoupler module, wherein the negative electrode and the positive electrode of the input end are respectively connected to the output end of the comparator and the connection point of the two pull-up resistors; the output end of the optocoupler module is connected to the control module;

[0012] A power IC control module, whose output end is connected to the enable end of the power IC and whose input end is connected to the output end of the comparator, is used to set the enable end of the power IC to a low level to shut down the power IC when its input end is at a high level.

[0013] A further improvement of the present invention is that the input voltage module comprises:

[0014] Two diodes, whose anodes are respectively connected to the two pins of the AC input end, and whose cathodes are both connected to the first end of the third resistor; the second end of the third resistor is the output end of the input voltage module;

[0015] The filtering circuit includes a sixth capacitor, a ninth resistor and a tenth resistor; the ninth resistor is connected in series with the tenth resistor, and the two are connected in parallel with the sixth capacitor after being connected in series; one end of the sixth capacitor is grounded, and the other end is connected to the second end of the third resistor.

[0016] A further improvement of the present invention is that the filter circuit is connected to a jitter elimination module; the jitter elimination module comprises:

[0017] The second transistor has a source connected to the ground, a drain connected to the connection point of the ninth resistor and the tenth resistor; an eleventh resistor connected between the gate and the source; and a gate connected to the output end of the comparator through the twelfth resistor.

[0018] A further improvement of the present invention is that the power supply module further includes a rectifier module, a transformer and an output filter module;

[0019] The input end of the rectifier module is connected to the AC input end, and the negative pole of the output end is grounded;

[0020] One end of the primary side of the transformer is connected to the positive electrode of the output end of the rectifier module, and the other end is connected to the power IC; the secondary side of the transformer is connected to the output filter module;

[0021] The VCC terminal is connected to a linear voltage stabilizing module, and the input terminal of the linear voltage stabilizing module is connected to the output terminal of the rectifier module.

[0022] A further improvement of the present invention is that the reference voltage module includes a controllable precision voltage regulator and a fourth capacitor; the anode of the controllable precision voltage regulator is grounded; the fourth capacitor is connected between the anode of the controllable precision voltage regulator and the reference terminal; the cathode of the controllable precision voltage regulator is connected to the reference terminal and the same-direction terminal of the comparator; the same-direction terminal of the comparator is connected to the VCC terminal through a fourth resistor.

[0023] A further improvement of the present invention is that the power IC control module comprises:

[0024] The MOS tube has a source connected to the ground and a drain connected to the enable terminal of the power IC;

[0025] The third capacitor and the first resistor are both connected between the source and the gate of the MOS tube;

[0026] The second resistor R2 has one end connected to the gate of the MOS tube, and the other end serving as the control end of the power IC control module connected to the output end of the comparator.

[0027] The advantages of the present invention are:

[0028] (1) It can continuously detect the input voltage of the AC input terminal and automatically shut down the power IC when the input voltage is undervoltage, and turn on the power IC when the input voltage is normal, thereby realizing undervoltage protection for the power IC and avoiding the problem of heating or even burning caused by long-term operation under low voltage;

[0029] (2) A jitter elimination module is used to make the input voltage at the AC input end have different undervoltage thresholds during the rising and falling processes, so that the main power switching detection circuit has a hysteresis characteristic, thereby avoiding power supply fluctuations caused by repeated switching of the main power and the backup power when the AC input voltage is near the undervoltage threshold;

[0030] (3) The circuit structure is simple and reliable. The input voltage module, comparator, and reference voltage module cooperate with each other to detect and judge the AC input voltage, avoiding the use of complex filtering and analog-to-digital conversion circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The schematic diagram of the main power conversion detection circuit of the shut-down power IC used in the power module. DETAILED DESCRIPTION

[0032] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0033] Example: Figure 1As shown, an embodiment of the present invention includes a main power conversion detection circuit for a power module that can shut down a power IC. The backup power conversion detection circuit is used for an AC-powered power module to monitor whether the input AC voltage of the power module is undervoltage, and to send a signal to the control module IC4 when the input AC voltage is undervoltage, prompting it to switch the power supply mode, and shut down the power IC ( Figure 1 IC1 in the circuit).

[0034] The power module involved in this embodiment includes: a power IC for chopping, a rectifier module, a transformer and an output filter module. Specifically, the rectifier module includes a rectifier bridge DB1 and an electrolytic capacitor C1. The input end of the rectifier module is connected to the AC input end, and the negative pole of its output end is grounded; the positive pole is connected to one end of the primary winding of the transformer T1, and the other end of its primary winding is connected to the power IC, and the power IC is used for chopping. The secondary side of the transformer T1 is connected to the output filter module. The output filter module includes a diode D1 and an electrolytic capacitor C2. The power IC has an enable terminal. When the enable terminal is at a low level, it is in a working state. When the enable terminal is at a high level or suspended, the power IC is in a working state.

[0035] like Figure 1 As shown, the main power conversion detection circuit of this embodiment includes: an input voltage module 1, a reference voltage module, a comparator IC3, an optical coupler module OP1, a power IC control module 2 and a jitter elimination module 3. Specifically:

[0036] The input voltage module 1 is connected to the AC input terminal of the power module, and includes a filter circuit composed of capacitors and resistors, which is used to convert the input voltage of the power module into pulsed direct current and output the pulsed direct current after voltage division.

[0037] In a specific embodiment, the input voltage module 1 includes two diodes D2 and D3, and the anodes of the diodes D2 and D3 are connected to the AC2 pin and the AC1 pin of the AC input terminal, respectively. The cathodes of the diodes D2 and D3 are connected to the first end of the third resistor R3. The second end of the third resistor R3 is the output end of the input voltage module 1. The filter circuit of the input voltage module 1 includes a sixth capacitor C6, a ninth resistor R9 and a tenth resistor R10. The ninth resistor R9 is connected in series with the tenth resistor R10 and then connected in parallel with the sixth capacitor C6. One end of the sixth capacitor C6 is grounded, and the other end is connected to the second end of the third resistor R3.

[0038] The reference voltage module is used to generate a reference voltage. The reference voltage module includes a controllable precision voltage regulator IC2 and a fourth capacitor C4. The controllable precision voltage regulator IC2 is implemented using a TL431 chip, whose anode is grounded, and the fourth capacitor C4 is connected between the anode of the controllable precision voltage regulator IC2 and the reference terminal. The cathode of the controllable precision voltage regulator IC2 is connected to the reference terminal and the same direction terminal of the comparator IC3. The same direction terminal of the comparator is connected to the VCC terminal through the fourth resistor R4.

[0039] In a specific embodiment, the output voltage of the reference voltage module and the input voltage module 1 should satisfy that when the input voltage of the AC input terminal is at the undervoltage critical value, the minimum value of the output voltage of the input voltage module 1 is equal to the output voltage of the reference voltage module. The reference voltage module is implemented using a TL431 chip, and its configuration method is a conventional technical means in this field. The input voltage module 1 is a circuit network composed of resistors and capacitors, and its output voltage can also be adjusted according to demand. Figure 1 A specific implementation is given in FIG. 1 , which shows the parameters of the reference voltage module and the components of the input voltage module 1. The undervoltage threshold value corresponding to the parameter is 165V.

[0040] The same-phase end of the comparator IC3 is connected to the output end of the reference voltage module, and its inverting end is connected to the output end of the input voltage module 1. The output end of the comparator IC3 is connected to the VCC end through two pull-up resistors R5 and R6 connected in series. When the input voltage of the AC input end is lower than the undervoltage critical value, the output end of the comparator IC3 is in a high-impedance state, and is affected by the pull-up resistors R5 and R6. At this time, the output end of the comparator IC3 is a high level; otherwise, the output end of the comparator IC3 is a low level.

[0041] The negative electrode and the positive electrode of the input end of the optocoupler module OP1 are respectively connected to the output end of the comparator IC3 and the connection points of the two pull-up resistors R5 and R6. The output end of the optocoupler module OP1 is connected to the control module IC4. When the input voltage of the AC input end is higher than the undervoltage critical value, the output end of the comparator IC3 is low level, and the two ends of the pull-up resistor R6 have a certain voltage, so that the optocoupler module emits light, so that the corresponding pin of the control module IC4 receives a high level signal. When the input voltage of the AC input end is lower than the undervoltage critical value, the output end of the comparator IC3 is in a high level state, and the optocoupler module OP1 does not emit light at this time, and the corresponding pin of the control module IC4 receives a low level signal. In this embodiment, the control module IC4 is an MCU, and the optocoupler can play an isolating role. The control module IC4 can switch the main and standby power according to the detection result of the main and standby power conversion detection circuit.

[0042] The structures of the power IC control module 2 and the jitter elimination module 3 are similar. Both are implemented by NMOS transistors, and the control terminals of both are connected to the output terminal of the comparator IC3. When the input voltage of the AC input terminal is lower than the undervoltage critical value, the output terminal of the comparator IC3 is at a high level, so that the NMOS of the power IC control module 2 and the jitter elimination module 3 are turned on.

[0043] In order to realize the above functions, in a specific embodiment, the power IC control module 2 includes a second resistor R2, a third capacitor C3, a first resistor R1 and a MOS tube Q1. The source of the MOS tube Q1 is grounded, and the drain is connected to the enable terminal of the power IC. The first resistor R1 and the third capacitor C3 are both connected between the source and the gate of the MOS tube Q1. One end of the second resistor R2 is connected to the gate of the MOS tube Q1, and the other end is connected to the output end of the comparator IC3 as the control end of the power IC control module 2. When the source and drain of the MOS tube Q1 are turned on, the enable end of the power IC is at a low level, and the power IC is in a closed state, otherwise the power IC is in a working state.

[0044] In a specific embodiment, the jitter elimination module 3 includes a second transistor Q2, whose source is grounded, and whose drain is connected to the connection point of the ninth resistor R9 and the tenth resistor R10; an eleventh resistor R11 is connected between its gate and source; and its gate is connected to the output end of the comparator IC3 through the twelfth resistor R12.

[0045] When the input voltage at the AC input end drops to the undervoltage critical value, since the voltage output by the input voltage module 1 is pulsating direct current, which has a DC component and an AC component, as the input voltage at the AC input end continues to drop, the voltage output by the input voltage module 1 will fluctuate around the output voltage of the reference voltage module, which will cause the state of the output end of the comparator IC3 to change repeatedly.

[0046] By introducing the jitter elimination module 3, when the input voltage drops below the undervoltage critical value for the first time, the output end of the comparator IC3 enters a high level state, so that the MOS tube Q2 in the jitter elimination module 3 is turned on. After the MOS tube Q2 is turned on, the two ends of the tenth resistor R10 in the input voltage module 1 are short-circuited, so that the sixth capacitor C6 is discharged quickly, and the voltage division ratio of the output end of the input voltage module 1 is reduced at the same time, so that the voltage value output by the input voltage module 1 is quickly reduced, and it is prevented from fluctuating up and down with the output voltage of the reference voltage module, resulting in repeated changes in the state of the output end of the comparator IC3.

[0047] When the input voltage at the AC input end is lower than the undervoltage critical value, the main and standby power conversion detection circuit of this embodiment can also detect whether the input voltage has recovered to above the undervoltage critical value. When the input voltage at the AC input end is higher than the undervoltage critical value, the output end of the comparator IC3 enters a low level state, and at the same time, the optocoupler module OP1 is turned on, the enable end of the power supply IC is set to zero to make it enter the working state, and the MOS tube Q2 in the jitter elimination module 3 changes from the on state to the off state. When the MOS tube Q2 changes to the off state, the voltage value output by the input voltage module 1 can be rapidly increased, so as to avoid the output voltage of the reference voltage module fluctuating up and down, causing the state of the output end of the comparator IC3 to change repeatedly.

[0048] In this embodiment, by using the jitter elimination module 3 and matching appropriate circuit parameters, when the input voltage of the AC input end rises to 175V AC, the main-standby power conversion detection circuit determines that the input AC voltage is greater than the undervoltage critical value, and controls the power supply IC to start; and when the input voltage of the AC input end drops to 165V AC, the main-standby power conversion detection circuit determines that the input AC voltage is lower than the undervoltage critical value, and controls the power supply IC to shut down. The use of the jitter elimination module 3 allows the input voltage of the AC input end to have different undervoltage critical values ​​during the rising process and the falling process, so that the main-standby power conversion detection circuit has a hysteresis characteristic, avoiding power supply fluctuations caused by repeated switching of the main and standby powers when the AC input voltage is near the undervoltage critical value.

[0049] The above embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modification, replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A main-standby power conversion detection circuit for a power supply IC that can be turned off for a power supply module, wherein the power supply module includes a power supply IC for chopping, and the power supply IC has an enable terminal, characterized in that The main power conversion detection circuit comprises: An input voltage module, connected to the AC input terminal of the power module, used to convert the input voltage of the power module into pulse direct current, and output the pulse direct current after voltage division; A reference voltage module, used for generating a reference voltage; A comparator, whose non-inverting end is connected to the output end of the reference voltage module, and whose inverting end is connected to the output end of the input voltage module; the output end of the comparator is connected to the VCC end through two pull-up resistors connected in series; An optocoupler module, wherein the negative electrode and the positive electrode of the input end are respectively connected to the output end of the comparator and the connection point of the two pull-up resistors; the output end of the optocoupler module is connected to the control module; A power IC control module, whose output end is connected to the enable end of the power IC, and whose input end is connected to the output end of the comparator, and is used to set the enable end of the power IC to a low level to shut down the power IC when its input end is at a high level; The input voltage module comprises: Two diodes, whose anodes are respectively connected to the two pins of the AC input end, and whose cathodes are both connected to the first end of the third resistor; the second end of the third resistor is the output end of the input voltage module; A filter circuit, comprising a sixth capacitor, a ninth resistor and a tenth resistor; the ninth resistor is connected in series with the tenth resistor, and the two are connected in parallel with the sixth capacitor; one end of the sixth capacitor is grounded, and the other end is connected to the second end of the third resistor; The reference voltage module includes a controllable precision voltage stabilizing source and a fourth capacitor; the anode of the controllable precision voltage stabilizing source is grounded; the fourth capacitor is connected between the anode of the controllable precision voltage stabilizing source and the reference terminal; the cathode of the controllable precision voltage stabilizing source is connected to the reference terminal and the same direction terminal of the comparator; the same direction terminal of the comparator is connected to the VCC terminal through a fourth resistor; The power IC control module includes: MOS tube, whose source is grounded and whose drain is connected to the enable terminal of the power IC; The third capacitor and the first resistor are both connected between the source and the gate of the MOS tube; A second resistor has one end connected to the gate of the MOS tube, and the other end serving as a control end of the power IC control module connected to the output end of the comparator.

2. A main power conversion detection circuit for a power IC that can be turned off for a power module according to claim 1, characterized in that: The filter circuit is connected to a jitter elimination module; the jitter elimination module comprises: The second transistor has a source connected to the ground, a drain connected to the connection point of the ninth resistor and the tenth resistor; an eleventh resistor connected between the gate and the source; and a gate connected to the output end of the comparator through the twelfth resistor.

3. A main power conversion detection circuit for a power IC that can be turned off for a power module according to claim 1, characterized in that: The power supply module also includes a rectifier module, a transformer and an output filter module; The input end of the rectifier module is connected to the AC input end, and the negative pole of the output end is grounded; One end of the primary side of the transformer is connected to the positive electrode of the output end of the rectifier module, and the other end is connected to the power IC; the secondary side of the transformer is connected to the output filter module; The VCC terminal is connected to a linear voltage stabilizing module, and the input terminal of the linear voltage stabilizing module is connected to the output terminal of the rectifier module.

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