An input overvoltage protection circuit with linear voltage regulation function

Abstract

This utility model discloses an input overvoltage protection circuit with linear voltage regulation function, applied to a charger including a transformer and a main switch chip. The input terminal of the main switch chip is connected to the same-name terminal of the primary winding of the transformer. The input overvoltage protection circuit includes an input overvoltage protection module, a fifth polarity capacitor, a second Zener diode, a second diode, and a nineteenth resistor. The input overvoltage protection module includes a first transistor. The collector of the first transistor is connected to the positive terminal of the fifth polarity capacitor (grounded at the negative terminal) and the output terminal of the second resistor group. The input terminal of the second resistor group is connected to the power input terminal, the high voltage terminal, and the opposite-name terminal of the primary winding of the transformer. The base of the first transistor is connected to the cathode of the second Zener diode (grounded at the anode). The collector and base of the first transistor are connected to the two ends of the nineteenth resistor. The emitter of the first transistor is connected to the operating voltage terminal of the main switch chip through the second diode.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to an input overvoltage protection circuit with linear voltage regulation function. Background Technology

[0002] To prevent damage to the main switching MOSFET due to excessive input voltage, chargers typically include an input overvoltage protection circuit. Existing input overvoltage protection circuits generally consist of a controllable precision voltage regulator, an NPN transistor, a Zener diode, and surface-mount resistors. By utilizing the voltage divider provided by the surface-mount resistors, the voltage reaches the reference value of the controllable precision voltage regulator, which then controls the transistor's conduction. This changes the voltage at the control chip pins, shutting off the main switching MOSFET and achieving the input overvoltage protection function. Traditional input overvoltage protection circuits only provide input overvoltage protection, offering only basic functionality. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide an input overvoltage protection circuit with linear voltage regulation function, so as to expand the function of the input overvoltage protection circuit.

[0004] To solve the above-mentioned technical problems, the purpose of this utility model is achieved through the following technical solution: A linear voltage regulation input overvoltage protection circuit is provided, applied to a charger. The charger includes a transformer and a main switching chip. The input terminal of the main switching chip is connected to the same-name terminal of the primary winding of the transformer. The linear voltage regulation input overvoltage protection circuit is connected to the power input terminal of the charger, the primary winding of the transformer, and the main switching chip, respectively. It includes an input overvoltage protection module, a fifth polarity capacitor, a second Zener diode, a second diode, and a nineteenth resistor. The input overvoltage protection module includes... The circuit includes a first transistor, the collector of which is connected to the positive terminal of the fifth polarity capacitor and the output terminal of the second resistor group. The input terminal of the second resistor group is connected to the power input terminal, the high voltage terminal, and the opposite terminal of the primary winding of the transformer. The negative terminal of the fifth polarity capacitor is grounded. The base of the first transistor is connected to the cathode of the second Zener diode. The anode of the second Zener diode is grounded. The collector and base of the first transistor are connected to the two ends of the nineteenth resistor. The emitter of the first transistor is connected to the operating voltage terminal of the main switch chip through the second diode.

[0005] The further technical solution is as follows: the input overvoltage protection module also includes a voltage divider module and a controllable precision voltage regulator. The reference electrode of the controllable precision voltage regulator is connected to the voltage divider module, the anode of the controllable precision voltage regulator is grounded, and the cathode of the controllable precision voltage regulator is connected to the base of the first transistor.

[0006] The further technical solution is as follows: the voltage divider module includes a first resistor group and a second resistor connected in series. The reference electrode of the controllable precision voltage regulator is connected to the series node of the first resistor group and the second resistor. The first end of the first resistor group is connected to the power input terminal, the high voltage terminal and the opposite terminal of the primary winding of the transformer, respectively. The second end of the first resistor group is connected to the first end of the second resistor. The second end of the second resistor is grounded.

[0007] The further technical solution is as follows: both the first resistor group and the second resistor group include three resistors connected in series in sequence.

[0008] The further technical solution is as follows: the collector of the first transistor is connected to the protection terminal of the main switch chip through the 27th resistor, the 10th capacitor and the 28th resistor connected in series in sequence, and the protection terminal of the main switch chip is also connected to the 29th grounding resistor.

[0009] The further technical solution is as follows: the positive terminal of the fifth polarity capacitor is connected to the same-name terminal of the auxiliary winding of the transformer through the third diode, and the opposite-name terminal of the auxiliary winding of the transformer is grounded.

[0010] The further technical solution is as follows: the cathode of the third diode is connected to the positive terminal of the fifth polarity capacitor, and the anode of the third diode is connected to the series node of the tenth capacitor and the twenty-eighth resistor, as well as the terminal of the auxiliary winding of the transformer.

[0011] The further technical solution is as follows: the feedback terminal of the main switch chip is connected to the twelfth grounding capacitor and the photodetector of the second optocoupler in parallel, and the light source of the second optocoupler is connected to the same terminal of the secondary winding of the transformer after passing through the current limiting resistor.

[0012] The further technical solution is as follows: the input terminal of the main switch chip is the drain terminal, the input terminal of the main switch chip is grounded through the twentieth resistor and the ninth capacitor connected in series, and the input terminal of the main switch chip is connected to the opposite terminal of the primary winding of the transformer through the first diode.

[0013] The further technical solution is as follows: the current detection terminal of the main switch chip is grounded after passing through the 25th resistor and the 30th resistor connected in series.

[0014] The beneficial technical effects of this utility model are as follows: The input overvoltage protection circuit with linear voltage regulation function of this utility model is provided by setting an input overvoltage protection module including a first transistor. The collector of the first transistor is connected to the positive terminal of the fifth polarity capacitor and the connection node of the second resistor group. The second resistor group is connected to the high voltage terminal. The negative terminal of the fifth polarity capacitor is grounded. The base of the first transistor is connected to the cathode of the second Zener diode with the anode grounded. The emitter of the first transistor is connected to the working voltage terminal of the charger's main switch chip through the second diode. This ensures that the voltage on the working voltage terminal of the main switch chip does not exceed the voltage regulation value of the second Zener diode, thereby achieving linear voltage regulation function. This ensures that the main switch chip operates within a safe range and avoids the problem of the main switch chip being subjected to large losses and overheating. Moreover, the input overvoltage protection module has an input overvoltage protection function, so that the input overvoltage protection circuit with linear voltage regulation function has both input overvoltage protection function and linear voltage regulation function, realizing functional expansion and high practicality. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The circuit diagram shows the specific application of the input overvoltage protection circuit with linear voltage regulation function provided in this embodiment of the utility model. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0018] Please see Figure 1 , Figure 1This is a circuit diagram illustrating the specific application of the input overvoltage protection circuit with linear voltage regulation provided in this embodiment of the present invention. The input overvoltage protection circuit 10 with linear voltage regulation is applied to a charger. The charger includes a transformer and a main switch chip U3. The input terminal of the main switch chip U3 is connected to the same-name terminal of the primary winding of the transformer. The input overvoltage protection circuit 10 with linear voltage regulation is connected to the power input terminal of the charger, the primary winding of the transformer, and the main switch chip U3. The input overvoltage protection circuit 10 with linear voltage regulation includes an input overvoltage protection module 11, a fifth polarity capacitor EC5, a second Zener diode ZD2, a second diode D2, and a nineteenth resistor R19. The input overvoltage protection module 11 includes a first transistor Q1, and the nineteenth resistor R19... The collector of transistor Q1 is connected to the positive terminal of the fifth polarity capacitor EC5 and the output terminal of the second resistor group 102. The input terminal of the second resistor group 102 is connected to the power input terminal, the high voltage terminal HV, and the opposite terminal of the primary winding of the transformer. The negative terminal of the fifth polarity capacitor EC5 is grounded. The base of the first transistor Q1 is connected to the cathode of the second Zener diode ZD2. The anode of the second Zener diode ZD2 is grounded. The collector and base of the first transistor Q1 are connected to the two ends of the nineteenth resistor R19, so that the nineteenth resistor R19 is connected between the collector and base of the first transistor Q1. The emitter of the first transistor Q1 is connected to the operating voltage terminal VDD of the main switch chip U3 through the second diode D2.

[0019] In this configuration, the anode of the second diode D2 is connected to the emitter of the first transistor Q1, and the cathode of the second diode D2 is connected to the operating voltage terminal VDD of the main switch chip U3. An eleventh grounding capacitor C11 is connected between the cathode of the second diode D2 and the operating voltage terminal VDD of the main switch chip U3. The power input terminal of the charger is an AC input terminal, which can be connected to the mains power. The AC positive terminal of the charger is connected to the live wire L, and the AC negative terminal of the charger is connected to the neutral wire N. The AC positive terminal of the charger is connected to the AC input positive terminal of the rectifier bridge BD1 through the fuse F1. The AC negative terminal of the charger is connected to the AC input negative terminal of the rectifier bridge BD1 through the thermistor NTC1. The DC output positive terminal of the rectifier bridge BD1 is connected to the high voltage terminal HV, the input terminal of the second resistor group, the input terminal of the input overvoltage protection module, and the opposite-name terminal of the primary winding of the transformer through the first inductor L1. The DC output negative terminal of the rectifier bridge BD1 is grounded through the third inductor L3. The positive and negative terminals of the DC output of rectifier bridge BD1 are connected to the positive and negative terminals of the second polarity capacitor EC2, respectively. The negative terminals of the first inductor L1 and the primary winding of the transformer are connected in parallel with the negative terminals of the third polarity capacitor EC3 and the fourth polarity capacitor EC4, which are grounded. The positive terminals of the second polarity capacitor EC2 and the third polarity capacitor EC3 are connected to the two ends of the second resistor R2, respectively. The negative terminals of the second polarity capacitor EC2 and the third polarity capacitor EC3 are connected to the two ends of the tenth resistor R10, respectively. The input overvoltage protection circuit 10 with linear voltage regulation function includes an input overvoltage protection module 11 comprising a first transistor Q1. The collector of the first transistor Q1 is connected to the positive terminal of the fifth polarity capacitor EC5 and the connection node of the second resistor group 102. The second resistor group 102 is connected to the high voltage terminal HV. The negative terminal of the fifth polarity capacitor EC5 is grounded. The base of the first transistor Q1 is connected to the cathode of the second Zener diode ZD2, which is grounded. The emitter of the first transistor Q1 is connected to the main switch chip of the charger via the second diode D2. The operating voltage terminal VDD of U3 is connected to ensure that the voltage on the operating voltage terminal VDD of the main switch chip U3 does not exceed the voltage regulation value of the second Zener diode ZD2, thus achieving linear voltage regulation. This ensures that the main switch chip U3 operates within a safe range and avoids the problem of the main switch chip U3 suffering from large losses and overheating. In addition, the input overvoltage protection module 11 has an input overvoltage protection function, so that the input overvoltage protection circuit 10 with linear voltage regulation function has both input overvoltage protection function and linear voltage regulation function, realizing functional expansion and high practicality.

[0020] Preferably, the input overvoltage protection module 11 further includes a voltage divider module 111 and a controllable precision voltage regulator U4. The reference electrode of the controllable precision voltage regulator U4 is connected to the voltage divider module 111, the anode of the controllable precision voltage regulator U4 is grounded, and the cathode of the controllable precision voltage regulator U4 is connected to the base of the first transistor Q1.

[0021] Specifically, in some embodiments, the voltage divider module 111 includes a first resistor group 101 and a second resistor R22 connected in series. The reference terminal of the controllable precision voltage regulator U4 is connected to the series node of the first resistor group 101 and the second resistor R22. The first end of the first resistor group 101 is connected to the power input terminal, the high voltage terminal HV, and the opposite terminal of the primary winding of the transformer, respectively. The second end of the first resistor group 101 is connected to the first end of the second resistor R22, and the second end of the second resistor R22 is grounded.

[0022] Specifically, both the first resistor group 101 and the second resistor group 102 include three resistors connected in series in sequence. The three resistors connected in series in the first resistor group 101 are denoted as R3, R6 and R11, and the three resistors connected in series in the second resistor group 102 are denoted as R4, R9 and R13.

[0023] Preferably, the collector of the first transistor Q1 is connected to the protection terminal PRT of the main switch chip U3 through the twenty-seventh resistor R27, the tenth capacitor C10, and the twenty-eighth resistor R28 connected in series. The protection terminal PRT of the main switch chip U3 is also connected to the twenty-ninth grounding resistor R29.

[0024] Specifically, the positive terminal of the fifth polarity capacitor EC5 is connected to the same-name terminal of the auxiliary winding of the transformer through the third diode D3, and the opposite-name terminal of the auxiliary winding of the transformer is grounded.

[0025] Specifically, the cathode of the third diode D3 is connected to the anode of the fifth polarity capacitor EC5, and the anode of the third diode D3 is connected to the series node of the tenth capacitor C10 and the twenty-eighth resistor R28, as well as the corresponding terminal of the auxiliary winding of the transformer.

[0026] Specifically, the feedback terminal FB of the main switch chip U3 is connected to the twelfth grounding capacitor C12 and the light receiver of the second optocoupler, which are connected in parallel. The light source of the second optocoupler is connected to the same-name terminal of the secondary winding of the transformer after passing through a current-limiting resistor.

[0027] Preferably, the input terminal of the main switch chip U3 is the drain terminal. The input terminal of the main switch chip U3 is grounded through a twentieth resistor R20 and a ninth capacitor C9 connected in series. The input terminal of the main switch chip U3 is connected to the opposite terminal of the primary winding of the transformer through a first diode D1. Specifically, a first resistor R1 and a seventh resistor R7 can be connected in series between the input terminal of the main switch chip U3 and the opposite terminal of the primary winding of the transformer through the first diode D1. The opposite terminal of the primary winding of the transformer is also connected to one end of the first capacitor C1. The other end of the first capacitor C1 is connected to the series connection point of the first resistor R1 and the seventh resistor R7. The other end of the first capacitor C1 is also connected to one end of the eighth resistor R8. The other end of the eighth resistor R8 is connected to the connection point of the first diode D1 and the seventh resistor R7.

[0028] Preferably, in some embodiments, the current detection terminal CS of the main switch chip U3 is grounded after being connected in series with the 25th resistor R25 and the 30th resistor R30.

[0029] Based on the above design, during operation, when the input voltage received at the charger's power input terminal is normal, the controllable precision voltage regulator does not work. When the voltage on the fifth polarity capacitor is less than the voltage regulation value of the second Zener diode, the first transistor conducts, supplying power to the main switch chip. The first transistor, the nineteenth resistor, the second Zener diode, and the second diode form a linear voltage regulator circuit. The fifth polarity capacitor is the input terminal of the linear voltage regulator circuit. When the voltage on the fifth polarity capacitor is less than the voltage regulation value of the second Zener diode, the collector and emitter of the first transistor conduct. The voltage on the eleventh capacitor is the voltage on the fifth polarity capacitor minus the forward voltage drop of the first transistor and then minus the forward voltage drop of the second diode. When the voltage on the fifth polarity capacitor is less than the voltage regulation value of the second Zener diode, the collector and emitter of the first transistor conduct. When the voltage across the capacitor exceeds the voltage regulation value of the second Zener diode, the first transistor reduces its conduction, making the voltage across the eleventh capacitor equal to the value of the second Zener diode. This ensures that the voltage at the operating voltage terminal of the main switch chip does not exceed the voltage regulation value of the second Zener diode, achieving linear voltage regulation. The voltage divider module divides the voltage between the first resistor group and the twenty-second resistor. When the input voltage received at the power input terminal of the charger is too high, the voltage across the twenty-second resistor increases with the increase of the input voltage. When the voltage across the twenty-second resistor reaches the reference voltage of the controllable precision voltage regulator, the first transistor turns off, and the operating voltage terminal of the main switch chip stops working due to undervoltage, thereby protecting the main switch chip and achieving input overvoltage protection.

[0030] In summary, the input overvoltage protection circuit with linear voltage regulation of this utility model, by setting an input overvoltage protection module including a first transistor, wherein the collector of the first transistor is connected to the positive terminal of the fifth polarity capacitor and the connection node of the second resistor group, the second resistor group is connected to the high voltage terminal, the negative terminal of the fifth polarity capacitor is grounded, the base of the first transistor is connected to the cathode of the second Zener diode with the anode grounded, and the emitter of the first transistor is connected to the working voltage terminal of the charger's main switch chip through the second diode, to ensure that the voltage at the working voltage terminal of the main switch chip does not exceed the voltage regulation value of the second Zener diode, thereby achieving linear voltage regulation, ensuring that the main switch chip operates within a safe range, and avoiding the problem of the main switch chip being subjected to large losses and overheating. Moreover, the input overvoltage protection module has an input overvoltage protection function, so that the input overvoltage protection circuit with linear voltage regulation function has both input overvoltage protection function and linear voltage regulation function, realizing functional expansion and high practicality.

[0031] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this utility model, and these modifications or substitutions should all be covered within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. An input overvoltage protection circuit with linear voltage regulation function, characterized in that, This invention relates to a charger, which includes a transformer and a main switching chip. The input terminal of the main switching chip is connected to the same-name terminal of the primary winding of the transformer. An input overvoltage protection circuit with linear voltage regulation is connected to the power input terminal of the charger, the primary winding of the transformer, and the main switching chip. The circuit includes an input overvoltage protection module, a fifth polarity capacitor, a second Zener diode, a second diode, and a nineteenth resistor. The input overvoltage protection module includes a first transistor. The collector of the first transistor is connected to the positive terminal of the fifth polarity capacitor and the output terminal of the second resistor group. The input terminal of the second resistor group is connected to the power input terminal, the high voltage terminal, and the opposite-name terminal of the primary winding of the transformer. The negative terminal of the fifth polarity capacitor is grounded. The base of the first transistor is connected to the cathode of the second Zener diode, and the anode of the second Zener diode is grounded. The collector and base of the first transistor are connected to both ends of the nineteenth resistor. The emitter of the first transistor is connected to the operating voltage terminal of the main switching chip through the second diode.

2. The input overvoltage protection circuit with linear voltage regulation function according to claim 1, characterized in that, The input overvoltage protection module also includes a voltage divider module and a controllable precision voltage regulator. The reference electrode of the controllable precision voltage regulator is connected to the voltage divider module, the anode of the controllable precision voltage regulator is grounded, and the cathode of the controllable precision voltage regulator is connected to the base of the first transistor.

3. The input overvoltage protection circuit with linear voltage regulation function according to claim 2, characterized in that, The voltage divider module includes a first resistor group and a 22nd resistor connected in series. The reference electrode of the controllable precision voltage regulator is connected to the series node of the first resistor group and the 22nd resistor. The first end of the first resistor group is connected to the power input terminal, the high voltage terminal and the opposite terminal of the primary winding of the transformer, respectively. The second end of the first resistor group is connected to the first end of the 22nd resistor, and the second end of the 22nd resistor is grounded.

4. The input overvoltage protection circuit with linear voltage regulation function according to claim 3, characterized in that, Both the first resistor group and the second resistor group include three resistors connected in series in sequence.

5. The input overvoltage protection circuit with linear voltage regulation function according to claim 1, characterized in that, The collector of the first transistor is connected to the protection terminal of the main switch chip via the 27th resistor, the 10th capacitor, and the 28th resistor connected in series. The protection terminal of the main switch chip is also connected to the 29th grounding resistor.

6. The input overvoltage protection circuit with linear voltage regulation function according to claim 5, characterized in that, The positive terminal of the fifth polarity capacitor is connected to the same-name terminal of the auxiliary winding of the transformer through the third diode, and the opposite-name terminal of the auxiliary winding of the transformer is grounded.

7. The input overvoltage protection circuit with linear voltage regulation function according to claim 6, characterized in that, The cathode of the third diode is connected to the positive terminal of the fifth polarity capacitor, and the anode of the third diode is connected to the series node of the tenth capacitor and the twenty-eighth resistor, as well as the corresponding terminal of the auxiliary winding of the transformer.

8. The input overvoltage protection circuit with linear voltage regulation function according to claim 1, characterized in that, The feedback terminal of the main switch chip is connected to the twelfth grounding capacitor and the photodetector of the second optocoupler, which are connected in parallel. The light source of the second optocoupler is connected to the same-name terminal of the secondary winding of the transformer after passing through a current-limiting resistor.

9. The input overvoltage protection circuit with linear voltage regulation function according to claim 1, characterized in that, The input terminal of the main switch chip is the drain terminal. The input terminal of the main switch chip is grounded through a twentieth resistor and a ninth capacitor connected in series. The input terminal of the main switch chip is connected to the opposite terminal of the primary winding of the transformer through a first diode.

10. The input overvoltage protection circuit with linear voltage regulation function according to claim 1, characterized in that, The current detection terminal of the main switch chip is grounded after passing through the 25th and 30th resistors connected in series.

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