Lamp turn-off circuit and power adapter

Abstract

The utility model relates to the technical field of power adapters, in particular to a light-off circuit and a power adapter. Comprising a first MOS tube, a second MOS tube and a voltage division module, a grid electrode of the first MOS tube is connected with a mains supply input end of the power adapter, a source electrode of the first MOS tube is grounded, a drain electrode of the first MOS tube and a grid electrode of the second MOS tube are both connected with a voltage output end of the voltage division module, a drain electrode of the second MOS tube is connected with a voltage input end of a PWM control chip in the power adapter, and a drain electrode of the first MOS tube is grounded. The source electrode of the second MOS tube is grounded, and the voltage input end of the voltage dividing module is connected with the primary side of a transformer in the power adapter; by designing the lamp turn-off circuit, after a user pulls out a power plug or turns off a power switch, the lamp turn-off circuit can quickly pull the voltage of the voltage input end of the PWM control chip to the ground, the PWM control chip stops working, energy stored by an electrolytic capacitor on the primary side of a transformer is prevented from being released to the secondary side of the transformer, and the power supply is turned off. Therefore, the secondary side of the transformer cannot obtain electric energy and the lamp can be quickly turned off.

Description

Technical Field

[0001] The utility model relates to the technical field of power adapters, in particular to a light-off circuit and a power adapter. Background Art

[0002] Currently, the power adapters or chargers on the market do not have the auxiliary function of turning off the power indicator light. When the user unplugs the power plug or turns off the power switch, the electrolytic capacitor on the primary side of the power supply will store energy. This energy will continue to be released to its secondary side through the transformer until the voltage is lower than the undervoltage value of the PWM control chip. The release will stop, causing the power indicator light to continue to be charged for about 60 seconds after the power is cut off, which will mislead the user that the power switch is not turned off.

[0003] Therefore, it is very important for those skilled in the art to design a light-off circuit and a power adapter that can turn off the light in time after the power is cut off. Utility Model Content

[0004] The technical problem to be solved by the embodiments of the present utility model is to provide a light-off circuit and a power adapter that can turn off the light in time after the power is cut off, so as to solve the problem in the prior art that the power indicator light cannot be turned off in time after the power is cut off.

[0005] The utility model discloses a light-off circuit, which is applied to a power adapter. The circuit comprises a first MOS transistor, a second MOS transistor and a voltage divider module. The gate of the first MOS transistor is connected to the mains input terminal of the power adapter, the source of the first MOS transistor is grounded, the drain of the first MOS transistor and the gate of the second MOS transistor are both connected to the voltage output terminal of the voltage divider module, the drain of the second MOS transistor is connected to the voltage input terminal of a PWM control chip in the power adapter, the source of the second MOS transistor is grounded, and the voltage input terminal of the voltage divider module is connected to the primary side of a transformer in the power adapter.

[0006] Optionally, a first rectifier module is further included, wherein a voltage input end of the first rectifier module is connected to the mains input end of the power adapter, and a voltage output end of the first rectifier module is connected to the gate of the first MOS tube.

[0007] Optionally, a first resistor is provided between the drain of the second MOS tube and the voltage input terminal of the PWM control chip in the power adapter.

[0008] Optionally, a second resistor is provided between the gate of the second MOS transistor and the voltage output end of the voltage divider module.

[0009] In order to solve the problems existing in the prior art, the present invention also provides a power adapter, which includes the light-off circuit as described above, and also includes a mains input end, a PWM control chip, a transformer, a charging control module and an indicator light module. The light-off circuit is respectively connected to the mains input end, the PWM control chip and the primary side of the transformer, the secondary side of the transformer is connected to the voltage input end of the charging control module, and the control end of the charging control module is connected to the indicator light module.

[0010] Optionally, a first energy storage module is provided on the primary side of the transformer, and an output end of the first energy storage module is connected to a voltage input end of the voltage divider module.

[0011] Optionally, a second energy storage module is provided on the secondary side of the transformer, and a voltage output terminal of the second energy storage module is connected to a voltage input terminal of the charging control module.

[0012] Optionally, a third MOS tube is provided between the control end of the charging control module and the indicator light module, the gate of the third MOS tube is connected to the control end of the charging control module, the source of the third MOS tube is grounded, and the drain of the third MOS tube is connected to the indicator light module.

[0013] Optionally, a toroidal inductor is provided between the second energy storage module and the charging control module.

[0014] Optionally, a second rectifier module is further included, wherein a voltage input end of the second rectifier module is connected to the mains input end, and a voltage output end of the second rectifier module is connected to the primary side of the transformer.

[0015] Compared with the prior art, the beneficial effect of the light-off circuit provided by the embodiment of the present invention is that: by designing a light-off circuit, when the user unplugs the power plug or turns off the power switch, the light-off circuit can quickly pull the voltage of the voltage input terminal of the PWM control chip to the ground, so that the PWM control chip stops working in time, effectively preventing the energy stored in the electrolytic capacitor on the primary side of the transformer from being released to its secondary side through the transformer, so that the secondary side of the transformer cannot obtain electrical energy and achieves a quick light-off effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which:

[0017] Figure 1 This is a circuit diagram of a light-off circuit provided by an embodiment of the utility model;

[0018] Figure 2 The circuit of the power adapter provided by the embodiment of the utility model Figure 1 ;

[0019] Figure 3 The circuit of the power adapter provided by the embodiment of the utility model Figure 2 . DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. Now, in conjunction with the accompanying drawings, a detailed description of the preferred embodiments of the present utility model will be given.

[0021] like Figures 1 to 3 As shown, the utility model provides a specific embodiment of a light-off circuit.

[0022] A light-off circuit, used in power adapter, reference Figure 1 The light-off circuit includes a first MOS transistor M1, a second MOS transistor M2, and a voltage divider module 100. The gate G of the first MOS transistor M1 is connected to the AC input terminal 10 of the power adapter, the source S of the first MOS transistor M1 is grounded, the drain D of the first MOS transistor M1 and the gate G of the second MOS transistor M2 are both connected to the voltage output terminal of the voltage divider module 100, the drain D of the second MOS transistor M2 is connected to the voltage input terminal of the PWM control chip 20 in the power adapter, the source S of the second MOS transistor M2 is grounded, and the voltage input terminal of the voltage divider module 100 is connected to the primary side of the transformer 30 in the power adapter.

[0023] Specifically, refer to Figure 1 The light-off circuit is applied to a charger or a power adapter to quickly turn off the power indicator light after the user unplugs the power plug or turns off the power switch to avoid misleading the user; the power adapter includes a mains input terminal 10 for receiving mains power, and the power adapter also includes a transformer 30 for converting the high-voltage AC power input from the mains input terminal 10 into the required low-voltage AC power. The transformer 30 includes a primary side and a secondary side, and the conversion between high voltage and low voltage is achieved through the change of the coils on the primary side and the secondary side. The secondary side of the transformer 30 is used to power the indicator light of the power adapter. The power adapter also includes a PWM control chip 20 for controlling the release of electrical energy on the primary side and the secondary side of the transformer 30.

[0024] Further, refer to Figure 1The light-off circuit includes a first MOS transistor M1, a second MOS transistor M2, and a voltage divider module 100. The first MOS transistor M1 is an NMOS transistor. When the gate G of the first MOS transistor M1 is at a high level, the first MOS transistor M1 is turned on. When the gate G of the first MOS transistor M1 is at a low level, the first MOS transistor M1 is turned off. The gate G of the first MOS transistor M1 is connected to the mains input terminal 10, and the source S of the first MOS transistor M1 is grounded. When the user unplugs the power plug or turns off the power switch, the voltage on the gate G side of the first MOS transistor M1 is almost 0, and the first MOS transistor M1 is not turned on.

[0025] Further, refer to Figure 1 The voltage input terminal of the voltage divider module 100 is connected to the primary side output terminal of the transformer 30, the voltage output terminal of the voltage divider module 100 is connected to the gate G of the second MOS transistor M2, the drain D of the second MOS transistor M2 is connected to the voltage input terminal of the PWM control chip 20 in the power adapter, and the source S of the second MOS transistor M2 is grounded. When the first MOS transistor M1 is turned off, the voltage stored in the electrolytic capacitor on the primary side of the transformer 30 and the divided voltage of the voltage divider module 100 are both applied to the gate G of the second MOS transistor M2, so that the second MOS transistor M2 When the second MOS transistor M2 is turned on, since the drain D of the second MOS transistor M2 is connected to the voltage input terminal of the PWM control chip 20 in the power adapter and the source S of the second MOS transistor M2 is grounded, when the second MOS transistor M2 is turned on, the voltage of the voltage input terminal of the PWM control chip 20 in the power adapter will be pulled to the ground, thereby causing the PWM control chip 20 in the power adapter to stop working, and further causing the energy stored in the electrolytic capacitor on the primary side of the transformer 30 to no longer be released to its secondary side through the transformer 30, thereby causing the indicator light on the secondary side of the transformer 30 to go out quickly.

[0026] Existing power adapters or chargers do not have an auxiliary function to turn off the power indicator light. When the user unplugs the power plug or turns off the power switch, the electrolytic capacitor on the primary side of the power transformer will store energy. This energy will continue to be released to its secondary side through the transformer until the voltage falls below the undervoltage value of the PWM control chip. The release will stop, causing the power indicator light to continue to be charged for about 60 seconds after the power is cut off before turning off, which will mislead the user that the power switch is not turned off.

[0027] In this embodiment, by designing a light-off circuit, when the user unplugs the power plug or turns off the power switch, the light-off circuit can quickly pull the voltage of the voltage input terminal of the PWM control chip to the ground, so that the PWM control chip stops working in time, effectively preventing the energy stored in the electrolytic capacitor on the primary side of the transformer from being released to its secondary side through the transformer, so that the secondary side of the transformer cannot obtain electrical energy and achieves a quick light-off effect.

[0028] In one embodiment, reference Figure 1 The voltage divider module 100 includes a resistor R69, a resistor R70, and a resistor R71, and the resistor R69, the resistor R70, and the resistor R71 are all connected in series.

[0029] In one embodiment, reference Figure 1 The light-off circuit further includes a first rectifier module 200 , a voltage input terminal of the first rectifier module 200 is connected to the AC input terminal 10 of the power adapter, and a voltage output terminal of the first rectifier module 200 is connected to the gate G of the first MOS tube M1 .

[0030] Specifically, refer to Figure 1 The first rectifier module 200 includes a rectifier diode D1, which is used to convert an AC signal into a unidirectional DC signal. It can also prevent current from flowing in the reverse direction, thereby protecting other electronic components. In this embodiment, the voltage input end of the first rectifier module 200 is connected to the AC input end 10 of the power adapter. When the user unplugs the power plug or turns off the power switch, there will be no voltage input to the AC input end 10. Then, the voltage rectified by the rectifier diode D1 is almost 0. The voltage output end of the first rectifier module 200 is connected to the gate G of the first MOS tube M1. The first MOS tube M1 will not conduct because its gate G is pulled low.

[0031] In one embodiment, reference Figure 1 A first resistor R72 is provided between the drain D of the second MOS tube M2 and the voltage input terminal of the PWM control chip 20 in the power adapter.

[0032] Specifically, refer to Figure 1 One end of the first resistor R72 is connected to the voltage input end of the PWM control chip 20, and the other end of the first resistor R72 is connected to the drain D of the second MOS transistor M2. When the second MOS transistor M2 is turned on, the voltage input end of the PWM control chip 20 will be quickly pulled to ground through the first resistor R72, and the PWM control chip 20 stops working.

[0033] In one embodiment, reference Figure 1 A second resistor R67 is provided between the gate G of the second MOS transistor M2 and the voltage output end of the voltage dividing module 100 .

[0034] Specifically, refer to Figure 1One end of the second resistor R67 is connected to the voltage output end of the voltage divider module 100, and the other end of the second resistor R67 is connected to the gate G of the second MOS transistor M2. The voltage stored in the electrolytic capacitor on the primary side of the transformer 30 and the series divided voltage formed by the resistors R1, R2, and R3 in the voltage divider module 100 are applied to the gate G of the second MOS transistor M2 through the second resistor R67 (the divided voltage value is greater than the turn-on voltage of the second MOS transistor M2), causing the drain D and source S of the second MOS transistor M2 to be conductive, thereby quickly pulling the voltage input end of the PWM control chip 20 to ground, and the PWM control chip 20 stops working.

[0035] like Figure 2 and Figure 3 As shown, the utility model also provides a specific embodiment of a power adapter.

[0036] A power adapter, reference Figure 2 and Figure 3 The power adapter includes the light-off circuit as described above, and also includes a mains input terminal 10, a PWM control chip 20, a transformer 30, a charging control module 40 and an indicator light module 50. The light-off circuit is connected to the mains input terminal 10, the PWM control chip 20 and the primary side of the transformer 30 respectively. The control terminal of the PWM control chip 20 is connected to the primary side of the transformer 30, the secondary side of the transformer 30 is connected to the voltage input terminal of the charging control module 40, and the control terminal of the charging control module 40 is connected to the indicator light module 50.

[0037] Specifically, refer to Figure 2 The mains input terminal 10 is used to receive AC power from a power socket. The mains input terminal 10 is also provided with a filtering circuit and a protection circuit for filtering out noise, interference, and fluctuations in the power grid, thereby protecting the power adapter and the devices connected to the power adapter. The primary side of the transformer 30 is connected to the mains input terminal 10, and the secondary side of the transformer 30 is connected to the charging control module 40 for converting the high-voltage AC power input from the mains input terminal 10 into the low-voltage AC power required for charging. The voltage input terminal of the PWM control chip 20 is connected to the drain D of the second MOS transistor M2 in the light-off circuit 60 for controlling the stability and accuracy of the output voltage by adjusting the duty cycle and duty cycle of the power adapter.

[0038] Further, refer to Figure 3 The indicator light module 50 is used to display the working status and power-on status of the power adapter. The control end of the indicator light module 50 is connected to the control end of the charging control module 40 to control the switch of the indicator light through the charging control module 40.

[0039] When the user unplugs the power plug or turns off the power switch, the voltage on the gate G side of the first MOS transistor M1 in the light-off circuit is almost 0, and the first MOS transistor M1 is not conducting. When the first MOS transistor M1 is turned off, the voltage stored in the electrolytic capacitor on the primary side of the transformer 30 and the divided voltage of the voltage divider module 100 are both applied to the gate G of the second MOS transistor M2, causing the second MOS transistor M2 to be turned on. Since the drain D of the second MOS transistor M2 is connected to the voltage input terminal of the PWM control chip 20 in the power adapter, and the source S of the second MOS transistor M2 is grounded, when the second MOS transistor M2 is turned on, the voltage at the voltage input terminal of the PWM control chip 20 in the power adapter will be pulled to ground, thereby causing the PWM control chip 20 in the power adapter to stop working. In addition, the energy stored in the electrolytic capacitor on the primary side of the transformer 30 is no longer released to its secondary side through the transformer 30, causing the indicator light on the secondary side of the transformer 30 to be quickly turned off.

[0040] Furthermore, when the energy stored in the electrolytic capacitor on the primary side of the transformer 30 is no longer released to its secondary side through the transformer 30, since the secondary side of the transformer 30 is connected to the voltage input end of the charging control module 40, the charging control module 40 can detect the voltage on the secondary side of the transformer 30 through its voltage input end. When it is detected that the voltage on the secondary side of the transformer 30 is lower than the voltage required for the normal operation of the power adapter, the control end of the charging control module 40 will output the corresponding level to the indicator light module 50, so that the indicator light of the indicator light module 50 goes out.

[0041] In one embodiment, reference Figure 2 A first energy storage module is provided on the primary side of the transformer 30, and the output end of the first energy storage module is connected to the voltage input end of the voltage divider module 100; a second energy storage module is provided on the secondary side of the transformer 30, and the voltage output end of the second energy storage module is connected to the voltage input end of the charging control module 40.

[0042] Specifically, refer to Figure 2 The first energy storage module includes first electrolytic capacitors EC1 and EC2, the input ends of the first electrolytic capacitors EC1 and EC2 are connected to the voltage output end of the mains input end 10, and the output ends of the first electrolytic capacitors EC1 and EC2 are connected to the voltage input end of the voltage divider module 100. The second energy storage module includes a second electrolytic capacitor EC3 and a third electrolytic capacitor EC4, the second electrolytic capacitor EC3 and the third electrolytic capacitor EC4 are connected in parallel, and the output ends of the parallel connection are connected to the voltage input end of the charging control module 40.

[0043] In one embodiment, reference Figure 3A third MOS transistor M3 is provided between the control terminal GPIO1 of the charging control module 40 and the indicator light module 50. The gate G of the third MOS transistor M3 is connected to the control terminal GPIO1 of the charging control module 40, the source S of the third MOS transistor M3 is grounded, and the drain D of the third MOS transistor M3 is connected to the indicator light module 50.

[0044] Specifically, refer to Figure 3 When the energy stored in the electrolytic capacitor on the primary side of the transformer 30 is no longer released to its secondary side through the transformer 30, the voltage input terminal VCC of the charging control module 40 will detect that the voltage on the secondary side of the transformer 30 is lower than the voltage required for normal operation of the power adapter. The control terminal GPIO1 of the charging control module 40 will output a low level to the third MOS transistor M3, and the third MOS transistor M3 will be turned off, and the indicator light will go out, further accelerating the light-off speed.

[0045] In one embodiment, a toroidal inductor is provided between the second energy storage module and the charging control module 40 .

[0046] Specifically, the toroidal inductor is used for inductive coupling and step-up and step-down. The toroidal inductor can step up or step down the electrical signal output by the second energy storage module and transmit it to the charging control module 40. At the same time, it can also isolate the DC component between the second energy storage module and the charging control module 40 to achieve stable output.

[0047] In one embodiment, a second rectifier module is further included, wherein a voltage input terminal of the second rectifier module is connected to the mains input terminal 10 , and a voltage output terminal of the second rectifier module is connected to the primary side of the transformer 30 .

[0048] Specifically, the second rectifier module includes a full-wave rectifier bridge for rectification, which includes four diodes and is connected in a bridge configuration, which allows current to pass in two directions, so that the rectifier bridge can simultaneously utilize the AC signals of the positive half cycle and the negative half cycle to improve the rectification efficiency.

[0049] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Those skilled in the art may modify the technical solutions described in the above embodiments, or replace some of the technical features therein with equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A light-off circuit, used in a power adapter, characterized in that: The invention comprises a first MOS transistor, a second MOS transistor and a voltage divider module. The gate of the first MOS transistor is connected to the mains input terminal of the power adapter, the source of the first MOS transistor is grounded, the drain of the first MOS transistor and the gate of the second MOS transistor are both connected to the voltage output terminal of the voltage divider module, the drain of the second MOS transistor is connected to the voltage input terminal of the PWM control chip in the power adapter, the source of the second MOS transistor is grounded, and the voltage input terminal of the voltage divider module is connected to the primary side of the transformer in the power adapter.

2. The light-off circuit according to claim 1, characterized in that: It also includes a first rectifier module, the voltage input end of the first rectifier module is connected to the mains input end of the power adapter, and the voltage output end of the first rectifier module is connected to the gate of the first MOS tube.

3. The light-off circuit according to claim 1, characterized in that: A first resistor is provided between the drain of the second MOS tube and the voltage input terminal of the PWM control chip in the power adapter.

4. The light-off circuit according to claim 1, characterized in that: A second resistor is provided between the gate of the second MOS tube and the voltage output end of the voltage divider module.

5. A power adapter, characterized in that: It comprises a light-off circuit as described in any one of claims 1 to 4, and also comprises a mains input terminal, a PWM control chip, a transformer, a charging control module and an indicator light module, the light-off circuit is respectively connected to the mains input terminal, the PWM control chip and the primary side of the transformer, the secondary side of the transformer is connected to the voltage input terminal of the charging control module, and the control terminal of the charging control module is connected to the indicator light module.

6. The power adapter according to claim 5, wherein: A first energy storage module is provided on the primary side of the transformer, and an output end of the first energy storage module is connected to a voltage input end of the voltage dividing module.

7. The power adapter according to claim 5, wherein: A second energy storage module is provided on the secondary side of the transformer, and a voltage output end of the second energy storage module is connected to a voltage input end of the charging control module.

8. The power adapter according to claim 5, wherein: A third MOS transistor is provided between the control end of the charging control module and the indicator light module, the gate of the third MOS transistor is connected to the control end of the charging control module, the source of the third MOS transistor is grounded, and the drain of the third MOS transistor is connected to the indicator light module.

9. The power adapter according to claim 7, wherein: A toroidal inductor is provided between the second energy storage module and the charging control module.

10. The power adapter according to claim 5, wherein: It also includes a second rectifier module, wherein the voltage input end of the second rectifier module is connected to the mains input end, and the voltage output end of the second rectifier module is connected to the primary side of the transformer.

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