CN210927494U

CN210927494U - Overvoltage protection circuit and power supply device

Info

Publication number: CN210927494U
Application number: CN201921851389.5U
Authority: CN
Inventors: 吴永芳
Original assignee: Guangzhou Shiyuan Electronics Thecnology Co Ltd
Current assignee: Guangzhou Shiyuan Electronics Thecnology Co Ltd
Priority date: 2019-10-30
Filing date: 2019-10-30
Publication date: 2020-07-03
Anticipated expiration: 2029-10-30

Abstract

The utility model discloses an overvoltage crowbar and power supply unit. Wherein, overvoltage crowbar includes: the first voltage stabilizing unit is connected between a first primary winding of the transformer and a target pin of the chip so as to stabilize input voltage entering the target pin, wherein a second primary winding of the transformer is connected with a control pin of the chip, a secondary winding of the transformer is connected with electric equipment, and the chip outputs a pulse modulation signal through the control pin so as to change electric energy of the second primary winding; and the second voltage stabilizing unit is connected with the first voltage stabilizing unit in parallel, wherein the starting voltage of the second voltage stabilizing unit is greater than that of the first voltage stabilizing unit. The utility model provides a transformer among the correlation technique leak to feel the technical problem who triggers overvoltage protection by mistake.

Description

Overvoltage protection circuit and power supply device

Technical Field

The utility model relates to an overvoltage protection field particularly, relates to an overvoltage crowbar and power supply equipment.

Background

The electric equipment has rated working voltage, and the electric equipment can normally work only when being connected to power supply equipment matched with the working voltage of the electric equipment. Fig. 1 shows an overvoltage protection circuit in the related art, as shown in fig. 1, a primary winding of a transformer T is divided into a main winding N1 and an auxiliary winding N2, the main winding N1 is used for storing electric energy, and the stored electric energy is provided to a target pin of a chip U1, such as a power Vcc pin, through the auxiliary winding N2, and is converted into different voltages, such as 24V and 12V, through a secondary winding and a rectification module, and then is transmitted to a consumer. When the voltage converted by the secondary winding and the rectifying module exceeds a preset value, the voltage stabilizer Z is conducted, so that the current of the optocoupler P is increased, the dynamic resistance of the emitter and collector of the phototriode of the optocoupler is reduced, the voltage between the emitter and collector of the phototriode is reduced, and the enable pin mode of the chip U1 is lowered. At the moment, the duty ratio output by the chip U1 is reduced, and the conduction time of the field effect transistor is correspondingly reduced, so that the purpose of reducing the energy storage of the main winding N1 is achieved, the output voltage of the secondary winding is reduced, and the overvoltage protection is realized. However, the influence of the leakage inductance of the transformer T on the chip U1 is not considered in the above circuit, and the transient sharp rise of the voltage caused by the leakage inductance can easily trigger the over-voltage protection of the chip U1 by mistake.

Aiming at the technical problem that the leakage inductance of the transformer triggers the overvoltage protection by mistake in the related art, an effective solution is not provided at present.

SUMMERY OF THE UTILITY MODEL

The utility model provides an overvoltage crowbar and power supply unit to solve the leakage inductance of transformer among the correlation technique at least and trigger overvoltage crowbar's technical problem.

According to an aspect of the embodiments of the present invention, there is provided an overvoltage protection circuit, including: the first voltage stabilizing unit is connected between a first primary winding of the transformer and a target pin of the chip so as to stabilize input voltage entering the target pin, wherein a second primary winding of the transformer is connected with a control pin of the chip, a secondary winding of the transformer is connected with electric equipment, and the chip outputs a pulse modulation signal through the control pin so as to change electric energy of the second primary winding; and the second voltage stabilizing unit is connected with the first voltage stabilizing unit in parallel, wherein the starting voltage of the second voltage stabilizing unit is greater than that of the first voltage stabilizing unit.

Optionally, the first voltage regulation unit includes a linear voltage regulation module connected between the first primary winding and the target pin.

Optionally, the linear voltage regulation module includes a first switch, a first voltage regulator, and a first resistor, where a first end of the first switch is connected to the first primary winding, a second end of the first switch is connected to the target pin, the first resistor is connected between the first end of the first switch and a controlled end of the first switch, and the controlled end of the first switch is further grounded through the first voltage regulator.

Optionally, the first switch is a triode, and the first terminal and the second terminal of the first switch are a collector and an emitter, respectively.

Optionally, the first voltage stabilizing unit further includes a voltage dropping module and/or a first isolation module, and the voltage dropping module and/or the first isolation module are connected in series on a line from the first primary winding to the target pin.

Optionally, the second voltage regulation unit includes a second isolation module, and the second isolation module is connected in series on a line from the first primary winding to the target pin.

Optionally, the circuit further includes a second capacitor, and the second capacitor is connected between the target pin and ground.

Optionally, the circuit further comprises a rectifying module connected between the secondary winding and the consumer.

Optionally, the circuit further includes a second switch, a controlled terminal of the second switch is connected to the control pin, and a first terminal and a second terminal of the second switch are respectively connected to the second primary winding.

According to another aspect of the embodiments of the present invention, there is provided a power supply device, including any one of the overvoltage protection circuits described above.

In an embodiment of the present invention, the overvoltage protection circuit includes: the first voltage stabilizing unit is connected between a first primary winding of the transformer and a target pin of the chip so as to stabilize input voltage entering the target pin, wherein a second primary winding of the transformer is connected with a control pin of the chip, a secondary winding of the transformer is connected with electric equipment, and the chip outputs a pulse modulation signal through the control pin so as to change electric energy of the second primary winding; and the second voltage stabilizing unit is connected with the first voltage stabilizing unit in parallel, wherein the starting voltage of the second voltage stabilizing unit is greater than that of the first voltage stabilizing unit. Compared with the prior art, the influence of the leakage inductance of the transformer on the chip is reduced through the first voltage stabilizing circuit, the second voltage stabilizing voltage of which the starting voltage is greater than the first voltage stabilizing circuit is used, the technical problem that the leakage inductance of the transformer triggers the overvoltage protection by mistake in the related art is solved, the purpose of rapidly reaching the overvoltage protection point voltage of the chip through the second voltage stabilizing unit branch is achieved, and the electric equipment is effectively protected.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without undue limitation to the invention. In the drawings:

FIG. 1 is a block diagram of an alternative over-voltage protection circuit of the related art;

fig. 2 is a schematic diagram of an alternative overvoltage protection circuit according to embodiment 1 of the present application; and

fig. 3 is a circuit diagram of an alternative overvoltage protection circuit according to embodiment 1 of the present application;

wherein the figures include the following reference numerals:

1-a first voltage stabilization unit; 2-a second voltage stabilization unit; 3-an overvoltage protection circuit; u1-chip; a T-transformer; n1 — main winding; n2 — auxiliary winding; a Z-potentiostat; a P-optical coupler; q1 — first switch; z1 — first regulator; z2-second regulator; r1 — first resistance; r2 — second resistance; r3 — third resistance; r4-fourth resistor; r5-fifth resistor; c1 — first capacitance; d1 — first diode; d2 — second diode; d3-third diode.

Detailed Description

In order to make the technical solution of the present invention better understood, the technical solution of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts shall belong to the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Example 1

Before describing further details of embodiments of the present application, an alternative overvoltage protection circuit that can be used to implement the principles of the present application will be described with reference to fig. 2. In its most basic configuration, fig. 2 is a schematic diagram of an overvoltage protection circuit in accordance with an embodiment of the present invention. For descriptive purposes, the circuit configuration depicted is only one example of a suitable environment and is not intended to suggest any limitation as to the scope of use or functionality of the application. Neither should the circuitry be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in fig. 2.

As shown in fig. 2, the overvoltage protection circuit 3 provided in the present embodiment includes:

and a first voltage stabilizing unit 1 connected between a first primary winding of the transformer T and a target pin of the chip U1 to stabilize an input voltage into the target pin, wherein a second primary winding of the transformer T is connected with a control pin of the chip U1, a secondary winding of the transformer T is connected with a power-consuming device, and the chip outputs a pulse modulation signal through the control pin to change electric energy of the second primary winding.

In an alternative, the first voltage stabilizing unit may stabilize a voltage entering the target pin within a preset range, where the voltage within the preset range may ensure normal operation of the chip; the first primary winding may be an auxiliary winding of a transformer, and the second primary winding may be a main winding of the transformer; the target pin can be any pin requiring level input on the chip, such as a power supply Vcc pin, a current feedback pin, a voltage feedback pin, and the like; the chip can be a Pulse Width Modulation (PWM) chip; the control pin may be a PWM output pin of the chip.

Generally, an input pin of a chip, such as a power Vcc pin, has a limit of a maximum voltage and a minimum voltage, and a protection function of the chip needs to be activated when the input pin is lower than the minimum voltage or higher than the maximum voltage. However, the primary winding of the transformer, and particularly the auxiliary winding in the primary winding, can generate leakage inductance that cannot be coupled to the secondary winding, resulting in a sharp increase in voltage into the Vcc pin, false activation of the chip over-voltage protection function, and disruption of the normal operation of the chip. Therefore, the first voltage stabilizing unit is arranged between the auxiliary winding of the transformer and the target pin, and the influence of leakage inductance on the chip can be eliminated.

It should be noted that, the first voltage stabilizing unit may include a first capacitor, and the first capacitor may filter the ac voltage in the first primary winding, so that the voltage entering the target pin is more stable; the first capacitor may be one or more, and may be disposed across the first primary winding or between the target pin and ground.

And the second voltage stabilizing unit 2 is connected in parallel with the first voltage stabilizing unit 1, wherein the starting voltage of the second voltage stabilizing unit 2 is greater than the starting voltage of the first voltage stabilizing unit 1.

In an alternative, the second voltage stabilizing unit may include a voltage stabilizing diode, a controllable precision voltage stabilizing source, and the like.

After the first voltage stabilizing unit is arranged, no matter how high the voltage of the first primary winding is, the overvoltage protection function of the chip cannot be started. Therefore, the present application also provides a second voltage stabilization unit between the first primary winding and the target chip.

Still referring to fig. 2, the auxiliary winding (not shown) of the transformer provides power to the power Vcc pin of the chip U1 through the first voltage regulation unit, and the first voltage regulation unit 1 can stabilize the voltage of the power Vcc pin within a predetermined range. In order to overcome the problem that the first voltage stabilizing unit 1 cannot start overvoltage protection due to shielding of an excessive voltage, the second voltage stabilizing units 2 are arranged at two ends of the first voltage stabilizing unit 1. Because the turn-on voltage of the second voltage stabilization unit 2 is greater than the turn-on voltage of the first voltage stabilization unit 1, the output voltage of the auxiliary winding is input to the target pin through the first voltage stabilization unit 1 under the non-overvoltage condition; under the overvoltage condition, the target pin is raised to the voltage of an overvoltage protection point through the conduction of the second voltage stabilizing unit 2, so that the overvoltage protection function of the chip U1 is started. The chip U1 can reduce the on-time of the fet by reducing the PWM duty cycle, thereby reducing the electric energy of the primary winding of the transformer, and further reducing the electric energy output from the secondary winding of the transformer to the electric device.

In the above embodiment, the overvoltage protection circuit includes: the first voltage stabilizing unit is connected between a first primary winding of the transformer and a target pin of the chip so as to stabilize input voltage entering the target pin, wherein a second primary winding of the transformer is connected with a control pin of the chip, a secondary winding of the transformer is connected with electric equipment, and the chip outputs a pulse modulation signal through the control pin so as to change electric energy of the second primary winding; and the second voltage stabilizing unit is connected with the first voltage stabilizing unit in parallel, wherein the starting voltage of the second voltage stabilizing unit is greater than that of the first voltage stabilizing unit. Compared with the prior art, the influence of transformer leakage inductance on the chip is reduced through the first voltage stabilizing circuit, the second voltage stabilizing voltage which is larger than the first voltage stabilizing circuit is achieved through the starting voltage, the problem that overvoltage protection is achieved by pulling down the enabling pin of a target chip through the current change of the optical coupler in the related art, the technical problem that overvoltage protection is triggered by the leakage inductance of the transformer in a false mode is solved, the purpose that the overvoltage protection point voltage of the chip is rapidly reached through the branch of the second voltage stabilizing unit is achieved, and electric equipment is effectively protected.

Optionally, the first voltage regulation unit 1 further includes a linear voltage regulation module connected between the first primary winding and the target pin.

In an alternative, the linear voltage stabilizing module may include a linear voltage regulator, and the linear voltage regulator may convert the high voltage in the first primary winding into a dc low voltage, and has a fast reaction speed and a small voltage ripple.

Alternatively, fig. 3 shows a circuit diagram of an alternative overvoltage protection circuit. As shown in fig. 3, the linear regulator module includes a first switch Q1, a first regulator Z1, and a first resistor R1, wherein a first terminal of the first switch Q1 is connected to the first primary winding, a second terminal of the first switch Q1 is connected to the target pin, a first resistor R1 is connected between a first terminal of the first switch Q1 and a controlled terminal of the first switch Q1, and the controlled terminal of the first switch Q1 is further grounded through a first regulator Z1.

In an alternative, the first switch may be a three-terminal switching device, such as an electronic switch, a triode, etc.; the first voltage stabilizer can be a voltage stabilizing diode, a controllable precise voltage stabilizing source and the like. For example, in the case where the first switch is an NPN type transistor, the first terminal and the second terminal of the first switch are a collector and an emitter, respectively.

Specifically, when the voltage input to the linear voltage stabilization module by the first primary winding reaches the turn-on voltage of the first voltage regulator, the first voltage regulator is turned on, and thereafter, the first voltage regulator maintains the turn-on voltage unchanged no matter how the voltage of the first primary winding rises. The first resistor has a voltage applied thereto, and the first resistor supplies a voltage for turning on the first switch to turn on the first switch. Meanwhile, the voltage of the first voltage stabilizer is constant after the first voltage stabilizer is conducted, so that the voltage entering the target pin can be maintained within a preset range.

Optionally, the first voltage stabilizing unit 1 further includes a voltage dropping module and/or a first isolation module, and the voltage dropping module and/or the first isolation module are connected in series on a line from the first primary winding to the target pin.

In an alternative, the voltage reduction module may include a resistor; the first isolation module may include one or more diodes that conduct in a single direction.

It should be noted that the voltage dropping module may be formed by one or more resistors in series-parallel connection, and may also include an adjustable resistor. For example, as shown in fig. 3, the voltage dropping module includes a third resistor R3, a fourth resistor R4, a fifth resistor R5 connected in parallel, and a second resistor R2 connected in series with three parallel resistors R3-R5. The first isolation block includes diodes D1-D2, and a diode D1 and a diode D2 are connected in series between the input terminal and the output terminal of the first voltage stabilization unit 1.

Optionally, the second voltage stabilizing unit 2 further includes a second isolation module, and the second isolation module is connected in series on a line from the first primary winding to the target pin.

In an alternative, the second isolation module may also include a diode conducting in a single direction.

As shown in fig. 3, a diode D3 is connected in series in the branch including the second voltage stabilization unit 2.

In an alternative, the second capacitor may include one or more capacitors, which are mainly used to ensure that the voltage entering the target pin is more stable.

In an alternative, the rectifying module may be composed of a diode.

In an alternative, the second switch may be a three-terminal switching device, such as an electronic switch, a field effect transistor, or the like. For example, in the case where the second switch is an N-channel fet, the first terminal and the second terminal of the second switch are a source and a drain, respectively.

The operation of the overvoltage protection circuit is explained in detail below. Still taking fig. 3 as an example, for convenience of description, several test point voltages are defined: the voltage between the first capacitor C1 and the first diode D1 is defined as a point a voltage, the voltage between the third diode D3 and the second regulator Z2 is defined as a point B voltage, and the voltage between the second diode D2 and the target pin is defined as a point C voltage. A second voltage regulator Z2 is connected in series between the point B and the power supply Vcc pin, and a first switch Q1 is connected in series between the point A and the power supply Vcc pin. The PN junction voltage of the collector and the emitter of the first switch Q1 is 0.7V, and the regulated voltage of the second regulator Z2 is 8.2V.

When the circuit is in no-load or light-load, the voltage at the point A is basically equal to the voltage at the point B, the first switch Q1 is in a saturation working state, and the voltage-stabilizing voltage of the second voltage stabilizer Z2 is far greater than the PN junction voltage of the first switch Q1, so that the second voltage stabilizer Z2 cannot work. When the circuit is fully loaded or overloaded, the voltage at the point a and the voltage at the point B can only reach 28V at the maximum, the regulated voltage output by the first voltage regulation unit 1, namely the voltage at the point C, is 22V at the minimum, the voltage between the voltage at the point B and the point C is 6V at the maximum, and the second voltage regulator Z2 does not work because 6V is less than 8.2V. When the output voltage of the auxiliary winding N2 is very large, the voltage at the point a and the voltage at the point B simultaneously rise linearly, and the maximum voltage can reach 36V. Since 36V-22V is 14V, and 14V is greater than the turn-on voltage of the zener diode of the second regulator Z2, 8.2V, when the zener diode of the second regulator Z2 is turned on, the target pin can reach the overvoltage protection point voltage. When the voltage of the target pin received by the chip U1 exceeds the voltage of the overvoltage protection point, the chip U1 outputs the reduced PWM duty ratio, and reduces the turn-on time of the field effect transistor, so that the electric energy of the main winding N1 of the transformer T is reduced, and the output voltage of the transformer T is ensured not to be increased sharply.

In the above embodiments of the present application, the overvoltage protection circuit includes: the first voltage stabilizing unit is connected between a first primary winding of the transformer and a target pin of the chip so as to stabilize input voltage entering the target pin, wherein a second primary winding of the transformer is connected with a control pin of the chip, a secondary winding of the transformer is connected with electric equipment, and the chip outputs a pulse modulation signal through the control pin so as to change electric energy of the second primary winding; and the second voltage stabilizing unit is connected with the first voltage stabilizing unit in parallel, wherein the starting voltage of the second voltage stabilizing unit is greater than that of the first voltage stabilizing unit. Compared with the prior art, the influence of the leakage inductance of the transformer on the chip is reduced through the first voltage stabilizing circuit, the second voltage stabilizing voltage of which the starting voltage is greater than the first voltage stabilizing circuit is used, the technical problem that the leakage inductance of the transformer triggers the overvoltage protection by mistake in the related art is solved, the purpose of rapidly reaching the overvoltage protection point voltage of the chip through the second voltage stabilizing unit branch is achieved, and the electric equipment is effectively protected. It is easy to note that the first voltage stabilizing unit adopts a linear voltage stabilizing module, and can stabilize the output voltage of the first primary winding within a preset range; the isolation modules are arranged on the first voltage stabilizing unit branch and the second voltage stabilizing unit branch, so that the voltage of a target pin can be prevented from flowing reversely; the voltage reduction module is arranged on the first voltage stabilization unit branch, so that the voltage supplied to the target pin can be in a proper range; the voltage supplied to the target pin can be more stabilized by a capacitor provided between the target pin and ground.

Example 2

According to the utility model provides an embodiment provides a power supply unit, including any one overvoltage crowbar in embodiment 1.

The above embodiment numbers of the present invention are only for description, and do not represent the advantages and disadvantages of the embodiments.

In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to the related descriptions of other embodiments.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. An overvoltage protection circuit, comprising:

the first voltage stabilizing unit is connected between a first primary winding of a transformer and a target pin of a chip so as to stabilize input voltage entering the target pin, wherein a second primary winding of the transformer is connected with a control pin of the chip, a secondary winding of the transformer is connected with electric equipment, and the chip outputs a pulse modulation signal through the control pin so as to change electric energy of the second primary winding;

and the second voltage stabilizing unit is connected with the first voltage stabilizing unit in parallel, wherein the starting voltage of the second voltage stabilizing unit is greater than the starting voltage of the first voltage stabilizing unit.

2. The circuit of claim 1, wherein the first voltage regulation unit comprises a linear voltage regulation module connected between the first primary winding and the target pin.

3. The circuit of claim 2, wherein the linear regulator module comprises a first switch, a first regulator, and a first resistor, wherein,

the first end of the first switch is connected with the first primary winding, the second end of the first switch is connected with the target pin, the first resistor is connected between the first end of the first switch and the controlled end of the first switch, and the controlled end of the first switch is grounded through the first voltage stabilizer.

4. The circuit of claim 3, wherein the first switch is a triode and the first and second terminals of the first switch are a collector and an emitter, respectively.

5. The circuit of claim 1, wherein the first voltage regulation unit further comprises a voltage reduction module and/or a first isolation module, and wherein the voltage reduction module and/or the first isolation module are connected in series on a line from the first primary winding to the target pin.

6. The circuit of claim 1, wherein the second voltage regulation unit comprises a second isolation module connected in series on the line from the first primary winding to the target pin.

7. The circuit of claim 1, further comprising a second capacitor connected between the target pin and ground.

8. The circuit of claim 1, further comprising a rectification module connected between the secondary winding and the powered device.

9. The circuit of claim 1, further comprising a second switch, wherein a controlled terminal of the second switch is connected to the control pin, and a first terminal and a second terminal of the second switch are respectively connected to the second primary winding.

10. A power supply device characterized by comprising an overvoltage protection circuit according to any one of claims 1 to 9.