An adaptively controlled X-capacitor active discharge circuit

Abstract

The present invention provides an adaptively controlled X-capacitor active discharge circuit, comprising: an AC-DC power supply main module, an X-capacitor rectified and current-limited to a high-voltage startup power supply terminal, connected to a power supply terminal via a high-voltage startup circuit, and connected to a VCC capacitor; a voltage monitoring module for detecting the output voltage of the high-voltage startup power supply terminal and outputting a power-on detection signal, a power-on type detection signal, and a power-off detection signal; an X-capacitor discharge control module for outputting a discharge control signal; and an X-capacitor discharge module comprising: a high-voltage startup unit for charging the VCC capacitor; and a discharge unit for discharging the X-capacitor and the VCC capacitor in response to the discharge control signal. Advantageous effects: Regardless of whether the input is AC or DC, active discharge can be performed quickly and effectively when the input loses power, clamping the voltages at the high-voltage startup power supply terminal and the power supply terminal to a relatively low safety range while eliminating the effects of reverse leakage current from the rectifier bridge.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to an adaptively controlled X-capacitor active discharge circuit. Background Art

[0002] To mitigate electromagnetic interference (EMI) in AC / DC switching power supplies, an EMI filter circuit is typically installed at the input. This filter circuit typically consists of an X-type filter capacitor (hereinafter referred to as the X-capacitor), connected in parallel between the live and neutral wires of the AC power input. This capacitor absorbs differential-mode EMI noise and typically has a capacitance in the uF range. When the AC power plug at the input of an AC / DC switching power supply is disconnected from the grid, a residual charge remains on the X-capacitor, potentially carrying high voltage. If a person accidentally touches the power plug, a discharge circuit is formed, potentially resulting in an electric shock. To address the dangers of live plugs, the national standard GB4943.1-2011 stipulates that the discharge time constant of Type A pluggable devices (such as power adapters) must not exceed 1 second, and the residual voltage of the capacitor after 1 second of discharge must not exceed 37% of its initial value. Therefore, a fast discharge circuit for the X-capacitor is necessary.

[0003] In existing technology, a high-resistance resistor is typically connected in parallel across the X-capacitor to form a discharge circuit. When the AC power at the switching power supply input is disconnected, the parallel discharge resistor discharges the residual charge on the X-capacitor, thereby ensuring that the switching power supply complies with safety regulations. However, since the discharge resistor is always connected in parallel across the X-capacitor, this solution will generate very significant no-load losses when the switching power supply is in no-load mode, significantly affecting the power supply's no-load efficiency. For example, in a mobile phone fast-charging power supply application, a 0.33uF X-capacitor needs to be discharged through a 1.5Meg parallel resistor when the input power is lost, resulting in approximately 70mW of loss across the resistor. With the increasingly stringent standby power requirements for switching power supplies, traditional solutions are unable to meet the latest energy consumption requirements. Therefore, how to actively discharge the X-capacitor in accordance with safety certification requirements while minimizing power consumption in the discharge circuit during normal operation remains a challenge.

[0004] While traditional solutions for passive X-capacitor discharge with parallel resistors suffer from high no-load losses, they do have the advantage of discharging the X-capacitors during power outages, regardless of AC or DC power supply conditions. However, current active X-capacitor discharge solutions in the industry generally only discharge the X-capacitors during AC power outages, but are unable to actively and rapidly discharge the X-capacitors during DC power outages. However, during the development phase of AC-DC power supplies, engineers often use DC sources instead of AC sources due to limited laboratory equipment. In this scenario, the X-capacitors cannot be effectively and rapidly discharged during a power outage, potentially exposing the power supply input to high voltage and potential component failure. Therefore, implementing active X-capacitor discharge in unconventional applications, such as AC-DC power supplies powered by DC sources, can reduce the risk of electric shock during the power supply development phase and effectively improve the reliability of the power supply throughout its lifecycle.

[0005] In low-power AC-DC power supply applications under 75 watts, electrolytic capacitors of tens to hundreds of uF are typically placed after the rectifier bridge for input voltage regulation and filtering. High-voltage startup or high-voltage detection for the main control chip typically draws power from the rectifier's X-capacitors located in front of the bridge. When the power supply is no-load and powered down, the electrolytic voltage behind the bridge is difficult to discharge quickly. During the discharge of the X-capacitors, a leakage current of the order of uA flows from the electrolytic capacitors behind the bridge to the input high-voltage detection circuit in front of the bridge. Failure to limit the residual voltage in the high-voltage detection circuit can easily disrupt the power-down sequence and cause false startups, impacting power supply reliability. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an adaptively controlled X-capacitor active discharge circuit.

[0007] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0008] An adaptively controlled X-capacitor active discharge circuit, comprising:

[0009] an AC-DC power supply main module, configured to charge an X capacitor, the X capacitor being connected between two ends of a power input terminal, the X capacitor being connected to a high-voltage startup power terminal via a first rectifier circuit and a first current limiting circuit, and the X capacitor being connected to a power supply terminal via a high-voltage startup circuit, the power supply terminal being connected to a VCC capacitor;

[0010] a voltage monitoring module connected to the high-voltage starting power supply terminal, configured to detect the output voltage of the high-voltage starting power supply terminal and output a power-on detection signal; and output a power-on type detection signal based on the power-on detection signal; and further configured to perform power-off detection and output a power-off detection signal;

[0011] An X-capacitor discharge control module, connected to the voltage monitoring module, configured to output a discharge control signal according to a power-off detection signal;

[0012] The X-capacitor discharge module includes: a high-voltage startup unit, connected to the voltage monitoring module, the high-voltage startup power supply terminal, and the power supply terminal, respectively, for charging the VCC capacitor when the power input terminal is just powered on and started; and a discharge unit, connected to the high-voltage startup unit and the power supply terminal, respectively, for discharging the X-capacitor and the VCC capacitor under the action of the discharge control signal.

[0013] Preferably, the high-voltage starting circuit includes:

[0014] An auxiliary power supply circuit, wherein the auxiliary power supply circuit is connected to a power supply pin of a controller chip through a second rectifier circuit, a current limiting filter circuit, and a linear voltage regulator circuit in sequence. The power supply pin is connected to the power supply end and to ground through the VCC capacitor, and is used to charge the VCC capacitor through the auxiliary power supply circuit after high-voltage startup is completed.

[0015] Preferably, the voltage monitoring module includes:

[0016] a power-on monitoring circuit, configured to compare the output voltage of the high-voltage starting power supply terminal with a preset voltage threshold and output the power-on detection signal;

[0017] a power-on type monitoring circuit, connected to the power-on monitoring circuit, for detecting a waveform period of the output voltage of the high-voltage starting power supply end, and when the output voltage has a waveform of more than one period, the power-on type detection signal indicates that the power-on type is alternating current; otherwise, it is direct current;

[0018] The power-off monitoring circuit is used to compare the sampling signal of the high-voltage starting power supply end with the low-frequency delay signal of the sampling signal and output the power-off detection signal.

[0019] Preferably, the voltage monitoring module further includes:

[0020] a first logic switch, wherein a fixed end of the first logic switch is connected to the high-voltage startup power supply end through a voltage sampling circuit, and a switching end of the first logic switch is switched between a discrete sampling switch and an inverting input of a first comparator;

[0021] The inverting input of the first comparator is also grounded through a first capacitor, the non-inverting input of the first comparator is connected to the power-off monitoring circuit, and the output of the first comparator is connected to the X-capacitor discharge control module.

[0022] Preferably, the voltage monitoring module further includes:

[0023] a second logic switch, wherein a fixed terminal of the second logic switch is grounded, and a switching terminal of the second logic switch is switched between an output of a second comparator and a non-inverting input terminal of a third comparator;

[0024] The non-inverting input terminal of the second comparator is connected to the high-voltage startup power supply terminal through a voltage sampling circuit, and the inverting input terminal of the second comparator is connected to a first fixed voltage threshold; the non-inverting input terminal of the third comparator is connected to the power supply terminal through a first current source, and the inverting input terminal of the third comparator is connected to a second fixed voltage threshold.

[0025] Preferably, the X-capacitor discharge control module further includes:

[0026] A timer circuit, connected to the power-on monitoring circuit, for timing and outputting a timing time;

[0027] a comparison circuit, connected to the timer circuit, for comparing the timing time with a set threshold value, and determining whether an input power failure occurs based on the comparison result;

[0028] The logic control circuit controls the discharge unit to discharge in response to the judgment result of the input power failure.

[0029] Preferably, the X-capacitor discharge control module includes:

[0030] a third logic switch, wherein a fixed terminal of the third logic switch is grounded, and a switching terminal of the third logic switch switches between an output of a logic gate circuit and an input of the timer circuit;

[0031] The logic gate circuit controls the third logic switch to switch in response to the output signal of the first comparator.

[0032] Preferably, the high-voltage starting unit comprises:

[0033] a regulating switch, wherein a gate of the regulating switch is connected to one end of a first resistor and to ground via a voltage regulator tube, a drain of the regulating switch is connected to the high-voltage startup power supply terminal via a first diode, and a source of the regulating switch is connected to the power supply terminal via a second diode;

[0034] a fourth logic switch, wherein a fixed end of the fourth logic switch is connected to the source of the regulating switch, and a switching end of the fourth logic switch switches between the output of the power-on type monitoring unit and the other end of the first resistor in response to the power-on type detection signal.

[0035] Preferably, the discharge unit includes:

[0036] A switching tube, wherein the gate of the switching tube is connected to the discharge control signal, and the drain of the switching tube is connected to the high-voltage startup unit and the power supply terminal through a pull-up resistor.

[0037] The advantages or beneficial effects of the technical solution of the present invention are:

[0038] The present invention can perform power-on detection, power-on type detection, and power-off detection, and adaptively switches circuit parameters based on the detection results. Regardless of whether the input is AC or DC, the X-capacitor can be quickly and effectively actively discharged when the input is powered off, and the residual voltage at the high-voltage starting power supply end is clamped within a safe low voltage range, eliminating the influence of the reverse leakage current of the rectifier bridge on the input high-voltage detection signal during the X-capacitor discharge process. The present invention is suitable for the field of AC-DC switching power supplies and can reduce system standby power consumption and improve the energy conversion efficiency of the power supply while meeting safety regulations. The system timing consistency after the power supply system is shut down and powered off under different operating conditions is effectively controlled, thereby improving the safety and reliability of the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a structural diagram of an adaptively controlled X-capacitor active discharge circuit in a preferred embodiment of the present invention;

[0040] Figure 2 Schematic diagram of waveforms showing the working process of active discharge of X-capacitors when input power is cut off and restored under AC power supply in a preferred embodiment of the present invention;

[0041] Figure 3 FIG. 1 is a waveform diagram of the working process of active discharge of the X capacitor when the input is powered off and powered on again under DC power supply in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0045] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, an adaptively controlled X-capacitor active discharge circuit is provided, which belongs to the field of integrated circuit technology. Figure 2 Shown, including:

[0046] AC-DC power supply main module 1, used to charge an X capacitor C19, the X capacitor is connected between two ends of a power input terminal, the X capacitor C19 is connected to a high-voltage startup power supply terminal HV via a first rectifier circuit and a first current limiting circuit, and the X capacitor C19 is connected to a power supply terminal VCC via a high-voltage startup circuit, and the power supply terminal is connected to a VCC capacitor C6;

[0047] The voltage monitoring module 2 is connected to the high-voltage starting power supply terminal, and is used to detect the output voltage of the high-voltage starting power supply terminal and output a power-on detection signal; and output a power-on type detection signal according to the power-on detection signal; and is also used to perform power-off detection and output a power-off detection signal;

[0048] The X-capacitor discharge control module 3 is connected to the voltage monitoring module 2 and is used to output a discharge control signal according to the power-off detection signal;

[0049] The X-capacitor discharge module 4 includes: a high-voltage startup unit, which is respectively connected to the voltage monitoring module, the high-voltage startup power supply terminal, and the power supply terminal, and is used to charge the VCC capacitor when the power input terminal is just powered on and started; a discharge unit, which is respectively connected to the high-voltage startup unit and the power supply terminal, and discharges the X-capacitor and the VCC capacitor under the action of a discharge control signal.

[0050] Specifically, in this embodiment, the adaptively controlled X-capacitor active discharge circuit includes four parts: an AC-DC power supply main module 1 , a voltage monitoring module 2 , an X-capacitor discharge control module 3 , and an X-capacitor discharge module 4 .

[0051] In the AC-DC power supply main module 1, an X capacitor is connected in parallel with both ends of the power input terminal. One end of the X capacitor is rectified and current-limited before being transferred to the high-voltage startup power supply terminal HV, serving as the high-voltage startup source for VCC. The other end of the X capacitor is connected to the power supply pin VCC of the controller chip U6 through a high-voltage startup circuit, serving as the power supply terminal. A VCC capacitor C6 is connected between the power supply pin VCC and ground. When the power input is powered on and high-voltage startup is completed, the high-voltage startup circuit provides charging energy for the VCC capacitor C6.

[0052] The voltage monitoring module 2 has the functions of monitoring input power-on, monitoring input power-off, and distinguishing between AC input power supply and DC input power supply. The input end of the voltage monitoring module 2 is connected to the high-voltage starting power supply end HV, and the output end is connected to the input of the X-capacitor discharge control module 3. It is used to adjust the structure and parameters of the voltage monitoring module 2 based on the monitoring result feedback of the power input power-on voltage type.

[0053] The X-capacitor discharge control module 3 controls the timer according to the output of the voltage monitoring module 2. The timer duration is compared with the set threshold value. The comparison result determines whether an input power failure has occurred, thereby deciding whether to perform active X-capacitor discharge.

[0054] The X-capacitor discharge module 4, when the power supply is initially powered on, provides a high-voltage charging path for the VCC capacitor via a high-voltage startup unit. Its input is connected to the high-voltage startup power supply terminal HV, and its output is connected to the anode of the VCC capacitor. A JFET or depletion-mode N-MOSFET is used as the regulating switch Q3 for the high-voltage startup power supply terminal HV. A Zener diode D19 is used to set the switch's off-point between the gate of regulating switch Q3 and ground. A resistor R40 is connected in series with a fourth logic switch S18 to clamp the voltage of the high-voltage startup power supply terminal HV. The on and off states of the fourth logic switch S18 are controlled by the power-on type monitoring results. The discharge unit is connected to the anode of the VCC capacitor via switch Q2 and a pull-up resistor R41. The gate of switch Q2 is controlled by the output of the X-capacitor discharge control module. When the input power is lost, the discharge unit regularly discharges the VCC capacitor, rapidly discharging the X-capacitor. Ultimately, the VCC voltage and the voltage of the high-voltage startup power supply terminal HV are clamped to a lower safety range by the VCC voltage.

[0055] Furthermore, the AC-DC power supply main module 1 includes: a first transformer TX3, the primary same-name terminal of the first transformer TX3 is connected to the L terminal through the resistor F1, the primary low-voltage terminal is connected to one end of the X capacitor, the other end of the X capacitor is connected to the secondary low-voltage terminal of the first transformer TX3, and the secondary same-name terminal of the first transformer TX3 is connected to the N terminal.

[0056] Furthermore, the first rectifier circuit uses bidirectional diodes D5 and D7 to achieve a rectification function, and the first current limiting circuit uses a resistor R32 to achieve current limiting.

[0057] As a preferred embodiment, the high voltage starting circuit includes:

[0058] Auxiliary power supply circuit, the auxiliary power supply circuit is connected to the power supply pin of a controller chip through a second rectifier circuit, a current limiting filter circuit and a linear voltage regulator circuit in sequence. The power supply pin is connected to the power supply end and grounded through the VCC capacitor C6. It is used to charge the VCC capacitor C6 through the auxiliary power supply circuit after the high-voltage startup is completed.

[0059] Specifically, the auxiliary power supply circuit uses a second transformer TX2 to implement the auxiliary power supply function. The same-name end of the second transformer TX2 is connected to the power supply pin VCC of the controller chip U6 after rectification, current limiting filtering, and linear voltage regulation. After the power input is powered on and high-voltage startup is completed, the charging energy of the VCC capacitor C6 is mainly provided by the second transformer TX2. Furthermore, when the power input is powered on and high-voltage startup is completed, the high-voltage startup unit provides charging energy for the VCC capacitor;

[0060] Furthermore, the high-voltage starting circuit may adopt an existing AC-DC switching power supply.

[0061] As a preferred embodiment, the voltage monitoring module 2 includes:

[0062] A power-on monitoring circuit is used to compare the output voltage of the high-voltage starting power supply terminal with a preset voltage threshold and output a power-on detection signal;

[0063] A power-on type monitoring circuit is connected to the power-on monitoring circuit and is used to detect the waveform period of the output voltage of the high-voltage starting power supply end, and when the output voltage is a waveform greater than one period, the power-on type detection signal indicates that the power-on type is AC; otherwise, it is DC;

[0064] The power-off monitoring circuit is used to compare the sampling signal of the high-voltage starting power supply end with the low-frequency delay signal of the sampling signal and output a power-off detection signal.

[0065] Specifically, the rectifier current-limiting voltage across the X capacitor is used to monitor input power-up, input voltage type, and input power-down. Input power-down monitoring is determined by comparing the input voltage sampling signal with its low-frequency (200Hz to 1kHz) delayed signal. When the input voltage is identified as DC, a small bias voltage (preferably in the range of -0.1mV to -0.1V) is used for input voltage slope detection; when the input voltage is identified as AC, a large bias voltage (preferably in the range of -10mV to -10V) is used for input voltage slope detection. Power-up monitoring detects input power-up by comparing the output voltage of the high-voltage startup power supply with a preset voltage threshold (minimum operating voltage threshold). A D-type flip-flop is used to detect whether the output voltage of the high-voltage startup power supply has an AC waveform of at least one cycle, thereby determining whether the input voltage type is AC and implementing power-up type monitoring.

[0066] Furthermore, the fourth comparator X1 is an op amp configured as an adder. When the input power-on type is detected as AC, the output of the fourth comparator X1 superimposes a large offset related to R5 / R9 on the small offset V36 (the magnitude of this offset is designed to be larger than that of V36). Compared to AC power-off detection, DC power-off is technically more difficult to detect, requiring a sufficiently small slope resolution for successful detection. Therefore, the detection strategy uses a small offset to detect voltage power-off for DC inputs and a large offset to detect voltage power-off for AC inputs. When the input power-on type is detected as DC, the output of the fourth comparator X1 only displays the value of the small offset V36.

[0067] The basic principle of power-off slope detection is to compare the discrete sample-and-hold signal of the original signal with the offset signal. If the result is consistently smaller than the offset for a long period of time, it indicates that the original signal has a negative slope. A prolonged negative slope of the HV signal is the fundamental characteristic and true sign of an input power-off. Input voltage slope detection allows real-time monitoring of input power-off recovery. After a power-off is detected, the X-capacitor discharge is initiated; after power-on, the X-capacitor discharge action is disabled.

[0068] As a preferred embodiment, the voltage monitoring module 2 further includes:

[0069] A first logic switch S2, wherein a fixed end of the first logic switch S2 is connected to a high-voltage startup power supply end through a voltage sampling circuit, and a switching end of the first logic switch S2 is switched between a discrete sampling switch V28 and an inverting input of a first comparator U120;

[0070] The inverting input of the first comparator U120 is also grounded through a first capacitor C1 , the non-inverting input of the first comparator U120 is connected to the power-off monitoring circuit, and the output of the first comparator U120 is connected to the X-capacitor discharge control module 3 .

[0071] Specifically, in this embodiment, the discrete sampling switch V28, the first logic switch S2, and the first capacitor C1C1 constitute a discrete sampling and holding circuit. The clock pulse signal source V28 controls the switch S2 to discretely sample the divided voltage signal of HV, and the signal is held at the negative input terminal of the comparator U120 through the first capacitor C1. Figure 2 The stepped waveform shown in HV_D.

[0072] As a preferred embodiment, the voltage monitoring module 2 further includes:

[0073] A second logic switch S22, wherein a fixed terminal of the second logic switch S22 is grounded, and a switching terminal of the second logic switch S22 is switched between an output of a second comparator U108 and a non-inverting input terminal of a third comparator U100;

[0074] The non-inverting input terminal of the second comparator U108 is connected to the high-voltage starting power supply terminal HV through the voltage sampling circuit, and the inverting input terminal of the second comparator U108 is connected to a first fixed voltage threshold BO_th; the non-inverting input terminal of the third comparator U100 is connected to the power supply terminal through a first current source I8, and the inverting input terminal of the third comparator U100 is connected to a second fixed voltage threshold Ct_BO_th.

[0075] Specifically, the voltage monitoring module 2 includes: a resistor R3, a resistor R4, a resistor R5, a resistor R9, a first logic switch S2, a second logic switch S22, an 800 Hz discrete sampling switch V28, a first capacitor C1, a second capacitor C17, a DC source V36, a first current source I8, a first comparator U120, a second comparator U108, a third comparator U100, a fourth comparator X1, a D flip-flop U175, a D flip-flop U177, a D flip-flop U3, a D flip-flop U5, a D flip-flop U110, an inverter U178, an inverter U180, an inverter U125, an inverter U7, an AND gate U172, and an OR gate U181.

[0076] Among them, the resistor R3 and the resistor R4 form a voltage sampling circuit, one end of the resistor R4 is connected to the high-voltage starting power supply end, the other end of the resistor R4 is grounded through the resistor R3, and the other end of the resistor R4 is connected to the positive electrode of the DC source V36, the negative electrode of the DC source V36 is connected to the non-inverting input end of the fourth comparator X1, the inverting input end of the fourth comparator X1 is connected to one end of the resistor R9 and is connected to the output of the fourth comparator X1 through the resistor R5, the output of the fourth comparator X1 is connected to the non-inverting input end of the first comparator U120, and the first comparator U120 The inverting input terminal of is grounded through the first capacitor C1, the fixed end of the first logic switch S2 is connected to the other end of the resistor R4, and the switching end of the first logic switch S2 is switched between the discrete sampling switch and the inverting input of the first comparator U120, and the HV input rectified steamed bun waveform is discretely sampled, and finally a stepped (non-smoothed) steamed bun waveform is obtained on the C1 capacitor, which is the negative input terminal of the comparator U120. By comparing the stepped steamed bun wave with the smooth steamed bun wave superimposed with DC bias, the purpose of detecting whether the input has a power failure can be achieved.

[0077] The clock control terminal of the D flip-flop U177 is connected to the output terminal of the first comparator U120, the D terminal of the D flip-flop U177 is connected to the QN terminal, the Q terminal of the D flip-flop U177 is connected to the clock control terminal of the D flip-flop U175, the QN terminal of the D flip-flop U177 is connected to the first terminal of the AND gate U172 through the inverter U178, the output of the inverter U178 is connected to the second terminal of the AND gate U172 through the inverter U180, and the output of the AND gate U172 is connected to the first terminal of the OR gate U181.

[0078] The non-inverting input terminal of the second comparator U108 is connected to the other end of the resistor R4, the inverting input terminal of the second comparator U108 is connected to the first fixed voltage threshold BO_th, the output terminal of the second comparator U108 is connected to the clock control terminal of the D flip-flop U3 through the inverter U7, the D terminal of the D flip-flop U3 is connected to the QN terminal, the Q terminal of the D flip-flop U3 is connected to the clock control terminal of the D flip-flop U5, the QN terminal of the D flip-flop U5 is connected to the input of the inverter U125, the output of the inverter U125 is connected to the other end of the resistor R9 in one way, and is connected to the second end of the OR gate U181 in the other way.

[0079] The non-inverting input of the third comparator U100 is connected to VCC via the first current source I8 and to ground via the second capacitor C17. The inverting input of the third comparator U100 is connected to the second fixed voltage threshold Ct_BO_th. The output of the third comparator U100 is connected to the clock control terminal of the D-type flip-flop U110. The fixed terminal of the second logic switch S22 is grounded, and the switching terminal of the second logic switch S22 switches between the output of the second comparator U108 and the non-inverting input of the third comparator U100, thereby adjusting the parameters of the voltage monitoring module 2.

[0080] As a preferred embodiment, the X-capacitor discharge control module 3 further includes:

[0081] A timer circuit, connected to the power-on monitoring circuit, is used to perform timing and output a timing time;

[0082] A comparison circuit, connected to the timer circuit, is used to compare the timing time with a set threshold value and determine whether an input power failure occurs based on the comparison result;

[0083] The logic control circuit controls the discharge unit to discharge in response to a judgment result of input power failure.

[0084] Specifically, to prevent power-off detection from being falsely triggered by other factors, embodiments of the present invention include a corresponding X-capacitor discharge delay circuit, which requires a timer. The logic for executing the X-capacitor discharge action from power-off detection is as follows: Even if an input voltage slope anomaly is detected, a sufficiently long wait period is required to rule out a power grid anomaly. If the observed input voltage slope remains abnormal during this period, the power grid anomaly can be ruled out, indicating that the input voltage slope anomaly is caused by a power outage, and the X-capacitor discharge action can be executed without risk.

[0085] As a preferred embodiment, the X-capacitor discharge control module 3 includes:

[0086] a third logic switch S21, wherein a fixed terminal of the third logic switch S21 is grounded, and a switching terminal of the third logic switch S21 switches between an output of a logic gate circuit and an input of a timer circuit;

[0087] The logic gate circuit controls the third logic switch S21 to switch in response to the output signal of the first comparator U120 .

[0088] Specifically, the X-capacitor discharge control module 3 includes: a third logic switch S21, a third capacitor C15, a second current source I6, a comparator U104, a comparator U98, a comparator U126, a D-type flip-flop U101, a D-type flip-flop U4, an OR gate U111, an AND gate U99, an AND gate U122, an AND gate U182, an inverter U8, an inverter U116, and an inverter U183.

[0089] The first input of the OR gate U111 is connected to the output of the first comparator U120, the second input of the OR gate U111 is connected to the output of the AND gate U99, and the third input of the OR gate U111 is connected to the output of the comparator U104; the non-inverting input of the comparator U104 is connected to VCC through the second current source I6, and the other is grounded through the third capacitor C15; the inverting input of the comparator U104 is connected to the third fixed threshold Ct_UP_th1, and the output of the comparator U104 is connected to the clock control terminal of the D flip-flop U101, and the R terminal of the D flip-flop U101 is connected to the clock control terminal of the D flip-flop U101. Connect the Q end of the D flip-flop U110, the Q end of the D flip-flop U101 is connected to the first input end of the AND gate U122, the first input end of the AND gate U182, the input of the inverter U183 and the first input end of the AND gate U99, the output of the inverter U183 is connected to the second input end of the AND gate U182, the output of the AND gate U182 is connected to the R ends of the above-mentioned D flip-flop U5, D flip-flop U175, and D flip-flop U177, the output of the inverter U183 is connected, and the other way is connected to the R end of the D flip-flop U110 and the R end of the D flip-flop U4 through the inverter U116.

[0090] The positive input of the comparator U98 is connected to the positive input of the comparator U104, the negative input of the comparator U98 is connected to the fourth fixed threshold Ct_UP_th2, and the output of the comparator U98 is connected to the second input of the AND gate U99; the output of the AND gate U99 is also connected to the clock control end of the D flip-flop U4 through the inverter U8, the D end and the QN end of the D flip-flop U4 are connected, and the Q end of the D flip-flop U4 is connected to the second input of the AND gate U122; the positive input of the comparator U126 is connected to VCC, the negative input of the comparator U126 is connected to the fifth fixed threshold VCC_off_th, the output of the comparator U126 is connected to the third input of the AND gate U122, and the output of the AND gate U122 is connected to the gate of the switch tube Q2 to control the on and off state of the switch tube Q2.

[0091] The fixed terminal of the third logic switch S21 is grounded, and the switching terminal of the third logic switch S21 switches between the output of the OR gate U111 and the non-inverting input terminal of the comparator U104 , thereby adjusting the parameters of the X-capacitor discharge control module 3 .

[0092] As a preferred embodiment, the high-voltage starting unit includes:

[0093] a regulating switch Q3, wherein the gate of the regulating switch Q3 is connected to one end of a first resistor R40 and to ground via a voltage regulator diode D19, the drain of the regulating switch Q3 is connected to the high-voltage startup power supply terminal HV via a first diode D18, and the source of the regulating switch Q3 is connected to the power supply terminal VCC via a second diode D25;

[0094] A fourth logic switch S18 has a fixed end connected to the source of the regulating switch Q3 and a switching end switched between the output of the power-on type monitoring unit and the other end of the first resistor R40 in response to the power-on type detection signal.

[0095] Specifically, a JFET or a depletion-mode N-MOSFET device is used as the adaptive regulating switch Q3 of the X-capacitor discharge path. By identifying whether the input power-on type is DC or AC, the control circuit structure and parameters (preferred range: R40 = 10kΩ ~ 10GΩ) between the gate and source of the regulating switch Q3 and the parameters of the power-off monitoring circuit output (preferred range: 0 ~ -10mV) are adaptively switched to maintain the input detection voltage from being affected by the reverse leakage current of the rectifier bridge.

[0096] As a preferred embodiment, the discharge unit includes:

[0097] A switch tube Q2, a gate of the switch tube Q2 is connected to a discharge control signal, and a drain of the switch tube Q2 is connected to a high-voltage startup unit HV and a power supply terminal VCC via a pull-up resistor R41.

[0098] Specifically, the discharge unit connects to the anode of the VCC capacitor via switch Q2 and pull-up resistor R41. The gate of switch Q2 is controlled by the output of the X-capacitor discharge control module. When the input power is lost, the VCC capacitor is regularly and intermittently discharged, rapidly discharging the X-capacitor. Ultimately, the VCC voltage and the voltage at the high-voltage startup power supply terminal HV are clamped to a low, safe range by the VCC voltage. Implementing ground discharge at the power supply terminal VCC has the advantage of clamping the high-voltage startup circuit and the input sampling voltage, eliminating the impact of reverse leakage current in the rectifier bridge.

[0099] Furthermore, the discharge current can be limited by adjusting the range of the pull-up resistor R41. The preferred range of the pull-up resistor R41 is 1kΩ to 20kΩ. For example, when R41 = 2k, the 20V VCC capacitor can be discharged, and the discharge current is 20V / 2kΩ = 10mA.

[0100] In the above preferred embodiment, the process of the adaptive control active discharge method is as follows: step S1, power on the power input; step S2, perform VCC high voltage startup; step S3, determine whether the VCC voltage reaches the normal operating range: if so, proceed to step S4 and step S5 respectively; if not, return to step S2; step S4, obtain the input power supply type and determine whether it is AC power: if so, switch the parameters of the voltage monitoring module 2 and the structure of the control circuit, and proceed to step S5; if not, directly proceed to step S5; step S5, perform power-off detection and determine whether the input is powered off: if so, perform X capacitor active discharge and VCC voltage maintenance control; if not, return to step S5 and re-perform power-off detection; step S6, perform power-on detection and determine whether the input is powered on: if so, return to step S2; if not, return to step S5.

[0101] In the above preferred embodiment, if Figure 2 As shown in FIG, a waveform diagram of the working process of the X-capacitor active discharge function when the input power is cut off and the input power is restored in a complete AC power supply condition in a preferred embodiment of the present invention. Figure 3 FIG. 1 is a waveform diagram of the working process of the X-capacitor active discharge function when the input is powered off and powered on again under a complete DC power supply condition in a preferred embodiment of the present invention.

[0102] The relevant waveform symbols are defined as follows:

[0103] SampleClk: V28 is used to control the clock signal of S2 for sampling.

[0104] UnPlug_Detect: Output of U101, power failure occurs and is detected.

[0105] Plug_In: This signal is considered to be a switch between the input grid L and N. When the switch is closed, the grid is connected to the circuit. When the switch is closed, the grid and the circuit are disconnected. This signal waveform is used to illustrate when power is lost and when power is restored.

[0106] Power_ON: Used to distinguish when the circuit is operating normally and when the X capacitor is discharged.

[0107] DC_ldentifly: indicates the voltage type detection result when the power-on type is DC input.

[0108] AC_ldentifly: indicates the voltage type detection result when the power-on type is AC input.

[0109] SlopDetect: Slope detection result. Output of comparator U120.

[0110] VCC_Level: Indicates whether the IC's Vcc voltage has reached a normal level. Because the entire X-capacitor discharge process must be completed under the premise that the IC can function normally, it is important to ensure that the IC's Vcc voltage is basically normal during the discharge process.

[0111] X2DC: Output of U122, control signal for executing X capacitor discharge action.

[0112] Ct_UP: Timer integration signal, voltage of C15.

[0113] HV_D: HV input detects the discrete sampling signal of the steamed bun wave and stores the voltage signal on C1.

[0114] V_X2: voltage across X capacitor C19.

[0115] I_UP_DC: is the active discharge current of Q2. The switch that performs X-capacitor discharge is Q2.

[0116] Vaux: The voltage used for power supply after rectification of the auxiliary winding of the transformer, and the voltage on capacitor C2.

[0117] T0-T9 represent critical moments.

[0118] like Figure 2 As shown, when AC power is input, the power supply starts to power on at time T0, and the power-on type is detected as DC. At time T1, the power-on type is detected as AC, and the structure of the voltage monitoring module 2 and the parameters of the input voltage slope detection are immediately switched through the above-mentioned logic switch. At time T2, the input power fails, and the input power failure is detected at time T3. The discharge unit is immediately controlled to intermittently discharge the VCC capacitor and the X capacitor. The discharge continues from T3 to T4 and stops from T4 to T5. The next intermittent discharge cycle begins at time T5, and the VCC voltage and the X capacitor voltage are discharged to the set safety range at time T8. At time T9, the input AC power is powered on again, and at time T10, the power-on type is detected as AC. Thereafter, real-time monitoring of the input to see if there is a power failure continues, and the cycle repeats.

[0119] like Figure 3As shown in the figure, with a DC input, the power supply begins to power up at T0, and the power-up type is detected as DC. At T2, the input loses power. This is detected at T3, and the discharge unit immediately controls the VCC capacitor and X capacitor to intermittently discharge. Discharge continues from T3 to T4, and ceases from T4 to T5. The next intermittent discharge cycle begins at T5, and continues until the VCC and X capacitor voltages are discharged to within the set safety range at T8. If the DC input is restored at T9, the power-up type is detected as DC at T10, and real-time monitoring is then performed to determine if the input has lost power. This cycle repeats.

[0120] The above technical solution has the following advantages or beneficial effects: the present invention can perform power-on detection, power-on type detection, and power-off detection, and adaptively switch circuit parameters based on the detection results. Regardless of whether the input is AC or DC, the X-capacitor can be quickly and effectively actively discharged when the input power is lost, and the residual voltage at the high-voltage starting power supply end is clamped within a safe low voltage range, eliminating the influence of the reverse leakage current of the rectifier bridge on the input high-voltage detection signal during the X-capacitor discharge process. The present invention is suitable for the field of AC-DC switching power supplies and can reduce system standby power consumption and improve the energy conversion efficiency of the power supply while meeting safety regulations. The system timing consistency after the power supply system is shut down and powered off under different operating conditions is effectively controlled, thereby improving the safety and reliability of the power supply system.

[0121] The above description is only a preferred embodiment of the present invention and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. An adaptively controlled X-capacitor active discharge circuit, characterized in that: include: an AC-DC power supply main module, configured to charge an X capacitor, the X capacitor being connected between two ends of a power input terminal, the X capacitor being connected to a high-voltage startup power terminal via a first rectifier circuit and a first current limiting circuit, and the X capacitor being connected to a power supply terminal via a high-voltage startup circuit, the power supply terminal being connected to a VCC capacitor; a voltage monitoring module connected to the high-voltage starting power supply terminal, configured to detect the output voltage of the high-voltage starting power supply terminal and output a power-on detection signal; and outputting a power-on type detection signal according to the power-on detection signal; and also being used to perform power-off detection and output a power-off detection signal; An X-capacitor discharge control module, connected to the voltage monitoring module, configured to output a discharge control signal according to a power-off detection signal; The X-capacitor discharge module includes: a high-voltage startup unit, connected to the voltage monitoring module, the high-voltage startup power supply terminal, and the power supply terminal, respectively, for charging the VCC capacitor when the power input terminal is just powered on and started; a discharge unit, connected to the high-voltage startup unit and the power supply terminal, respectively, for discharging the X-capacitor and the VCC capacitor under the action of the discharge control signal; The voltage monitoring module includes: a power-on monitoring circuit, configured to compare the output voltage of the high-voltage starting power supply terminal with a preset voltage threshold and output the power-on detection signal; a power-on type monitoring circuit, connected to the power-on monitoring circuit, for detecting a waveform period of the output voltage of the high-voltage starting power supply end, and when the output voltage has a waveform of more than one period, the power-on type detection signal indicates that the power-on type is alternating current; otherwise, it is direct current; A power-off monitoring circuit, configured to compare a sampling signal from a high-voltage starting power supply terminal with a low-frequency delayed signal of the sampling signal, and output the power-off detection signal; The voltage monitoring module further includes: a first logic switch, wherein a fixed end of the first logic switch is connected to the high-voltage startup power supply end through a voltage sampling circuit, and a switching end of the first logic switch is switched between a discrete sampling switch and an inverting input of a first comparator; The inverting input of the first comparator is also grounded through a first capacitor, the non-inverting input of the first comparator is connected to the power-off monitoring circuit, and the output of the first comparator is connected to the X-capacitor discharge control module.

2. The adaptively controlled X-capacitor active discharge circuit according to claim 1, characterized in that: The high-voltage starting circuit comprises: An auxiliary power supply circuit, wherein the auxiliary power supply circuit is connected to a power supply pin of a controller chip through a second rectifier circuit, a current limiting filter circuit, and a linear voltage regulator circuit in sequence. The power supply pin is connected to the power supply end and to ground through the VCC capacitor, and is used to charge the VCC capacitor through the auxiliary power supply circuit after high-voltage startup is completed.

3. The adaptively controlled X-capacitor active discharge circuit according to claim 1, characterized in that: The voltage monitoring module further includes: a second logic switch, wherein a fixed terminal of the second logic switch is grounded, and a switching terminal of the second logic switch is switched between an output of a second comparator and a non-inverting input terminal of a third comparator; The non-inverting input terminal of the second comparator is connected to the high-voltage startup power supply terminal through a voltage sampling circuit, and the inverting input terminal of the second comparator is connected to a first fixed voltage threshold; the non-inverting input terminal of the third comparator is connected to the power supply terminal through a first current source, and the inverting input terminal of the third comparator is connected to a second fixed voltage threshold.

4. The adaptively controlled X-capacitor active discharge circuit according to claim 1, characterized in that: The X-capacitor discharge control module further includes: A timer circuit, connected to the power-on monitoring circuit, for timing and outputting a timing time; a comparison circuit, connected to the timer circuit, for comparing the timing time with a set threshold value, and determining whether an input power failure occurs based on the comparison result; The logic control circuit controls the discharge unit to discharge in response to the judgment result of the input power failure.

5. The adaptively controlled X-capacitor active discharge circuit according to claim 4, characterized in that: The X-capacitor discharge control module includes: a third logic switch, wherein a fixed terminal of the third logic switch is grounded, and a switching terminal of the third logic switch switches between an output of a logic gate circuit and an input of the timer circuit; The logic gate circuit controls the third logic switch to switch in response to the output signal of the first comparator.

6. The adaptively controlled X-capacitor active discharge circuit according to claim 1, characterized in that: The high-voltage starting unit comprises: a regulating switch, wherein a gate of the regulating switch is connected to one end of a first resistor and to ground via a voltage regulator tube, a drain of the regulating switch is connected to the high-voltage startup power supply terminal via a first diode, and a source of the regulating switch is connected to the power supply terminal via a second diode; a fourth logic switch, wherein a fixed end of the fourth logic switch is connected to the source of the regulating switch, and a switching end of the fourth logic switch switches between the output of the power-on type monitoring unit and the other end of the first resistor in response to the power-on type detection signal.

7. The adaptively controlled X-capacitor active discharge circuit according to claim 1, characterized in that: The discharge unit includes: A switching tube, wherein the gate of the switching tube is connected to the discharge control signal, and the drain of the switching tube is connected to the high-voltage startup unit and the power supply terminal through a pull-up resistor.

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