Output overcurrent protection circuit and method based on multi-path output flyback high-voltage power supply

Abstract

The invention belongs to the technical field of circuits, and relates to an output overcurrent protection circuit and method based on a multi-path output flyback high-voltage power supply. According to the invention, the current of the corresponding output branch is acquired in real time through the plurality of output current acquisition circuits; the output over-current trigger circuit is used for comparing the collected current data with a preset threshold value and triggering an over-current protection mechanism once the collected current data exceed the threshold value, and each output branch is provided with an independent output over-current trigger circuit, so that accurate control can be conveniently realized; the over-current protection response circuit is used for gathering all signals output from the over-current trigger circuit, uniformly processing an over-current protection request, and sending an over-current protection signal to the PWM pulse width modulation slow start circuit when the over-current protection request occurs to trigger a power supply protection measure; the PWM pulse width modulation slow start circuit is used for completing soft start of the power supply after output over-current protection occurs in the output branch of any multi-path output flyback high-voltage power supply. And after the soft start is completed, if the current returns to normal, continuing to supply power.

Description

Technical Field

[0001] The invention belongs to the field of circuit technology, and relates to an output overcurrent protection circuit and method based on a multi-channel output flyback high-voltage power supply. Background Art

[0002] The current output overcurrent protection circuit of the multi-channel output flyback high-voltage power supply is generally: the signal of the primary current of the converter is collected through the current detection (CS) end of the PWM controller. When the flyback converter outputs overcurrent, it detects whether the primary current acquisition signal of the converter reaches the CS end protection threshold. If the protection threshold is reached, the converter outputs constant power, and its output voltages of each channel decrease to avoid further increase of the output current, thereby achieving output overcurrent protection. In view of the working characteristics of the multi-channel output flyback power supply, this overcurrent protection scheme has the following three main problems: 1. The output power of each output branch of a multi-output flyback high-voltage power supply is different, so the maximum current that each output branch can withstand is different, and the output overcurrent protection requirements of each output branch are also different. If the overcurrent protection method of the primary PWM controller CS end is adopted, the overcurrent protection threshold should cover the maximum operating current under all working conditions of the power supply and the overcurrent protection requirements of the maximum power output branch, so this threshold is generally large. If an overcurrent occurs in a small power output branch of the power supply, it may not reach the primary overcurrent protection threshold, resulting in over-current stress damage or even burning of the components of the output branch; 2. If the overcurrent protection method of the primary PWM controller CS end is adopted, when the overcurrent protection occurs, the converter will output constant power, and the output voltage of each channel will drop. When the overcurrent protection time is long, the output branches of the power supply will maintain low voltage output for a long time, which may cause the active power devices on the load side of the output to enter the linear working area, and the power devices will be damaged or even burned due to overpower consumption; In summary, the overcurrent protection method of the primary PWM controller CS end has the problems of low sensitivity, slow response speed and inability to meet the different overcurrent protection response requirements of each output branch of the flyback converter. Summary of the invention

[0003] The purpose of the present invention is to provide an output overcurrent protection circuit and method based on a multi-channel output flyback high-voltage power supply to solve the technical problem that the overcurrent protection sensitivity of the CS end of the primary side PWM controller is low, the response speed is slow, and the overcurrent protection response requirements of different output branches of the flyback converter cannot be met. The overcurrent protection of the present invention has good sensitivity and fast response speed, and can meet the different overcurrent protection response requirements of different output branches of the flyback converter.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses an output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply, comprising a plurality of output current acquisition circuits and a plurality of output overcurrent trigger circuits, each of which is respectively connected to an output overcurrent trigger circuit, and the plurality of output overcurrent trigger circuits are connected to a PWM pulse width modulation slow start circuit through the same overcurrent protection response circuit.

[0005] Furthermore, the output current acquisition circuit includes a current sensor, the current sensor is connected to an IV signal conversion unit, and the IV signal conversion unit is connected to an output overcurrent trigger circuit.

[0006] Furthermore, the IV signal conversion unit includes an IV signal conversion resistor, one end of the IV signal conversion resistor is respectively connected to the output overcurrent trigger circuit, the current sensor and the output current sampling signal interface, and the other end of the IV signal conversion resistor is grounded.

[0007] Further, the output overcurrent trigger circuit includes a comparator; The non-inverting terminal of the comparator is connected to the output current collection circuit through an RC voltage integration circuit; The non-inverting end of the comparator is connected to the output current collection circuit through the resistor R2, and the non-inverting end of the comparator is grounded through the capacitor C1; The inverting end of the comparator is connected to the power supply high level Vcc through resistors R3 and R5 in sequence, the anode of the Zener diode V1 is connected between the inverting end of the comparator and the resistor R3 through resistor R4, the cathode of the Zener diode V1 is connected between resistor R3 and resistor R5, the anode of the Zener diode V1 is grounded, the power supply input end of the comparator is connected to the power supply high level Vcc through resistor R6, the power supply input end of the comparator is connected to the output end of the comparator through resistor R7, the output end of the comparator is connected to the anode of the output combiner diode V2, and the cathode of the output combiner diode V2 is connected to the overcurrent protection response circuit.

[0008] Furthermore, the RC voltage integration circuit includes a resistor R2, one end of the resistor R2 is connected to the in-phase end of the comparator, the other end of the resistor R2 is connected to the output current acquisition circuit, and the in-phase end of the comparator and the resistor R2 are grounded via a capacitor C1.

[0009] Furthermore, the overcurrent protection response circuit includes a transistor Q2, the base of the transistor Q2 is connected to the output overcurrent trigger circuit, the base of the transistor Q2 is connected to the emitter of the transistor Q2 through a resistor R8 and an anti-interference capacitor C2, the emitter of the transistor Q2 is grounded, and the collector of the transistor Q2 is connected to the PWM pulse width modulation slow start circuit through a current limiting resistor R9.

[0010] Furthermore, the PWM pulse width modulation slow start circuit includes a transistor Q1, the collector of the transistor Q1 is connected to the base of the transistor Q1 through a capacitor C4 and a resistor R10 in sequence, the collector of the transistor Q1 and the capacitor C4 are grounded, the emitter of the transistor Q1 is connected to each other through the COMP end of the PWM pulse width modulator, the cathode of the diode V3 and the capacitor C3 respectively, the other end of the capacitor C3 and the anode of the diode V3 are both connected to the base of the transistor Q1, the Vref end of the PWM pulse width modulator is connected between the capacitor C4 and the resistor R10 through a resistor R12, the Vref end of the PWM pulse width modulator is connected to the cathode of the diode V4 through a resistor R11, and the anode of the diode V4 is connected between the capacitor C4 and the resistor R10.

[0011] Based on the above circuit, the present invention also discloses a working method of an output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply, comprising the following steps: The output current acquisition circuit collects the current signals of each branch of the flyback high-voltage power supply in real time, converts the current signals into voltage signals, and sends the voltage signals to the output overcurrent trigger circuit; If an output overcurrent occurs in any output branch of the flyback high-voltage power supply, after the voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit of the branch and lasts for a set time, the output overcurrent trigger circuit of the corresponding branch outputs an overcurrent protection trigger signal and sends the overcurrent protection trigger signal to the overcurrent protection response circuit; The overcurrent protection response circuit controls the output of the PWM pulse width modulation circuit to be turned off according to the overcurrent protection trigger signal, thereby turning off the output of the flyback high-voltage power supply, and synchronously discharging and resetting the PWM pulse width modulation slow start circuit; After the flyback high-voltage power supply completes output over-current protection, the flyback high-voltage power supply is soft-started through a PWM pulse width modulation slow-start circuit, and the flyback high-voltage power supply recovers to the output state before the over-current.

[0012] Furthermore, the steps of collecting the current signals of each branch of the flyback high-voltage power supply in real time through the output current collection circuit, converting the current signals into voltage signals, and sending the voltage signals to the output overcurrent trigger circuit are specifically as follows: The current signal of each branch of the flyback high-voltage power supply is collected in real time by a current sensor; The current signal is converted into a voltage signal through an IV signal conversion resistor, and the voltage signal is sent to the output overcurrent trigger circuit.

[0013] Furthermore, if an output overcurrent occurs in any output branch of the flyback high-voltage power supply, after the voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit of the branch and lasts for a set time, the output overcurrent trigger circuit of the corresponding branch outputs an overcurrent protection trigger signal, and the overcurrent protection trigger signal is sent to the overcurrent protection response circuit. The specific steps are as follows: If an output overcurrent occurs in any output branch of the flyback high-voltage power supply, the voltage signal reaches the protection threshold voltage of the comparator of the branch and lasts for a set time. Then, the comparator N1 outputs a high level, and the diode V2 is turned on, injecting current into the base of the transistor Q2 of the subsequent overcurrent protection response circuit.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention collects the current of the corresponding output branch in real time through several output current collection circuits to ensure that the collected current data is accurate and provide a basis for subsequent judgment; the output overcurrent trigger circuit is used to compare the collected current data with the preset threshold value. Once the threshold value is exceeded, the overcurrent protection mechanism is triggered. Each output branch has an independent output overcurrent trigger circuit, which is convenient for precise control and can meet the different overcurrent protection response requirements of each output branch of the flyback converter; the overcurrent protection response circuit is used to summarize the signals of all output overcurrent trigger circuits and uniformly process the overcurrent protection request. When the overcurrent protection request occurs, the overcurrent protection signal is sent to the PWM pulse width modulation slow start circuit to trigger the power supply protection measure; the PWM pulse width modulation slow start circuit is used to complete the soft start of the power supply after the output overcurrent protection occurs in any output branch of the multi-channel output flyback high-voltage power supply. After the soft start is completed, if the current returns to normal, the power supply continues. The overcurrent protection of the present invention has good sensitivity and fast response speed, and can meet the different overcurrent protection response requirements of each output branch of the flyback converter.

[0015] 2. The method of the present invention collects the current signals of each branch of the flyback high-voltage power supply in real time through the output current acquisition circuit, converts the current signal into a voltage signal, and sends the voltage signal to the output overcurrent trigger circuit, providing basic data for subsequent judgment and triggering; if any output branch of the flyback high-voltage power supply has an output overcurrent, the voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit of the branch and lasts for a set time, the output overcurrent trigger circuit of the corresponding branch outputs an overcurrent protection trigger signal, and sends the overcurrent protection trigger signal to the overcurrent protection response circuit, each branch has an independent overcurrent trigger circuit, and the overcurrent protection trigger signal is realized. Independent monitoring and protection of each branch prevents local faults from affecting the whole system. The overcurrent protection response circuit controls the output of the PWM pulse width modulation circuit to shut down according to the overcurrent protection trigger signal, thereby shutting down the output of the flyback high-voltage power supply to prevent the overcurrent from further deteriorating. It also discharges and resets the PWM pulse width modulation slow start circuit synchronously to prepare for the subsequent soft start, thus achieving comprehensive protection for the entire flyback high-voltage power supply and ensuring the safety of the power supply and load. After the flyback high-voltage power supply completes the output overcurrent protection, the flyback high-voltage power supply is soft-started through the PWM pulse width modulation slow start circuit, and the flyback high-voltage power supply returns to the output state before the overcurrent. The soft start is achieved through the PWM pulse width modulation slow start circuit, avoiding the impact and overcurrent problems that may be caused by direct start. The soft start process restores the power supply output to the state before the overcurrent, ensuring the stability and reliability of the power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The overall circuit structure diagram of the present invention; Figure 2 It is a circuit principle diagram of the present invention; Figure 3 The figure is a flow chart of the method of the present invention.

[0017] Among them: 1. Output current acquisition circuit; 2. Output overcurrent trigger circuit; 3. Overcurrent protection response circuit; 4. PWM pulse width modulation slow start circuit. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 creative work should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings: See also Figure 2 The present invention discloses an output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply, including a plurality of output current acquisition circuits 1 and a plurality of output overcurrent trigger circuits 2. Each output current acquisition circuit 1 is respectively connected to an output overcurrent trigger circuit 2. The plurality of output current acquisition circuits 1 are used to collect the current of the corresponding output branch in real time, ensure that the collected current data is accurate, and provide a basis for subsequent judgment, so as to ensure that the abnormal current situation is discovered in time and avoid further deterioration of the overcurrent situation. The output overcurrent trigger circuit 2 is used to compare the collected current data with a preset threshold value. Once the threshold value is exceeded, the overcurrent protection mechanism is triggered. Each output branch has an independent output overcurrent trigger circuit 2, which can realize precise control and avoid affecting the entire system due to a single branch failure. After detecting the overcurrent situation, it can respond quickly. The overcurrent protection has good sensitivity and fast response speed, which prevents damage to the power supply or load equipment, and can meet the different overcurrent protection response requirements of each output branch of the flyback converter. The plurality of output overcurrent trigger circuits 2 are connected to the PWM pulse width modulation slow start circuit 4 through the same overcurrent protection response circuit 3. The overcurrent protection response circuit 3 is used to aggregate the signals of all output overcurrent trigger circuits 2, uniformly process overcurrent protection requests, and send an overcurrent protection signal to the PWM pulse width modulation slow start circuit 4 when an overcurrent protection request occurs, triggering power supply protection measures. The PWM pulse width modulation slow start circuit 4 is used to complete the soft start of the power supply after the output overcurrent protection occurs in any output branch of the multi-channel output flyback high-voltage power supply. After the soft start is completed, if the current returns to normal, the power supply continues. The overcurrent protection of the present invention has good sensitivity and fast response speed, and can meet the different overcurrent protection response requirements of each output branch of the flyback converter.

[0021] Embodiment 1: See also Figure 2This embodiment discloses an output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply, including a plurality of output current acquisition circuits 1 and a plurality of output overcurrent trigger circuits 2, each output current acquisition circuit 1 is respectively connected to an output overcurrent trigger circuit 2, and a plurality of output overcurrent trigger circuits 2 are connected to a PWM pulse width modulation slow start circuit 4 through the same overcurrent protection response circuit 3; The PWM pulse width modulation slow start circuit 4 is used to complete the soft start of the power supply after the output over-current protection occurs in the output branch of any multi-channel output flyback high-voltage power supply.

[0022] Preferably, the output current acquisition circuit 1 includes a current sensor, the current sensor is connected to an IV signal conversion unit, and the IV signal conversion unit is connected to the output overcurrent trigger circuit 2.

[0023] Preferably, the IV signal conversion unit includes an IV signal conversion resistor, one end of which is respectively connected to the output overcurrent trigger circuit 2, the current sensor and the output current sampling signal interface, and the other end of the IV signal conversion resistor is grounded. The output current sampling signal interface is used to output the output current sampling signal IS.

[0024] Preferably, the output overcurrent trigger circuit 2 includes a comparator; The non-inverting terminal of the comparator is connected to the output current acquisition circuit 1 through an RC voltage integration circuit; The in-phase end of the comparator is connected to the output current acquisition circuit 1 through the resistor R2, and the in-phase end of the comparator is grounded through the capacitor C1; The inverting end of the comparator is connected to the power supply high level Vcc through resistors R3 and R5 in sequence, the inverting end of the comparator and the resistor R3 are connected to the anode of the Zener diode V1 through resistor R4, the cathode of the Zener diode V1 is connected between resistor R3 and resistor R5, the anode of the Zener diode V1 is grounded, the power supply input end of the comparator is connected to the power supply high level Vcc through resistor R6, the power supply input end of the comparator is connected to the output end of the comparator through resistor R7, the output end of the comparator is connected to the anode of the output combining diode V2, and the cathode of the output combining diode V2 is connected to the overcurrent protection response circuit 3.

[0025] Preferably, the RC voltage integration circuit includes a resistor R2, one end of the resistor R2 is connected to the in-phase end of the comparator, the other end of the resistor R2 is connected to the output current acquisition circuit 1, and the in-phase end of the comparator and the resistor R2 are grounded via a capacitor C1.

[0026] Preferably, the overcurrent protection response circuit 3 includes a transistor Q2, the base of the transistor Q2 is connected to the output overcurrent trigger circuit 2, the base of the transistor Q2 is connected to the emitter of the transistor Q2 through a resistor R8 and an anti-interference capacitor C2, the emitter of the transistor Q2 is grounded, and the collector of the transistor Q2 is connected to the PWM pulse width modulation slow start circuit 4 through a current limiting resistor R9.

[0027] Preferably, the PWM pulse width modulation slow start circuit 4 includes a transistor Q1, the collector of the transistor Q1 is connected to the base of the transistor Q1 through a capacitor C4 and a resistor R10 in sequence, the collector of the transistor Q1 and the capacitor C4 are grounded, the emitter of the transistor Q1 is connected to each other through the COMP end of the PWM pulse width modulator, the cathode of the diode V3 and the capacitor C3 respectively, the other end of the capacitor C3 and the anode of the diode V3 are both connected to the base of the transistor Q1, the Vref end of the PWM pulse width modulator is connected between the capacitor C4 and the resistor R10 through a resistor R12, the Vref end of the PWM pulse width modulator is connected to the cathode of the diode V4 through a resistor R11, and the anode of the diode V4 is connected between the capacitor C4 and the resistor R10.

[0028] Embodiment 2: The overall architecture design of this embodiment is as follows Figure 1 As shown, the overall architecture of the output overcurrent multi-threshold protection restart circuit based on the multi-output flyback high-voltage power supply includes several functional circuits such as a multi-output current acquisition circuit 1, a multi-output overcurrent trigger circuit 2, an overcurrent protection response circuit 3, and a PWM pulse width modulation slow start circuit 4. The functions of each circuit in the architecture are described below: Multi-channel output current acquisition circuit 1: It is composed of n-channel output current acquisition circuits 1, where n is the number of output channels of the multi-channel output flyback high-voltage power supply. The output current of each output branch of the multi-channel output flyback high-voltage power supply is collected through a current sensor, and the output current signal of each output branch is converted into an isolated sampling current signal, and the sampling current signal is converted into a voltage signal through an IV signal conversion resistor, and the voltage signal is sent to the multi-channel output overcurrent trigger circuit 2; Multi-channel output overcurrent trigger circuit 2: It is composed of n-channel output overcurrent trigger circuits 2, where n is the number of output channels of the multi-channel output flyback high-voltage power supply. The circuit receives the output current sampling voltage signal of each output branch of the multi-channel output flyback high-voltage power supply. When an output overcurrent occurs in any output branch of the power supply, its output current sampling voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit 2 of the branch and lasts for a period of time. The specific time is set according to the overcurrent protection requirements of the branch, and can reach the μs level at the fastest. The output overcurrent trigger circuit 2 of the branch responds and sends the overcurrent protection trigger signal to the overcurrent protection response circuit 3; Overcurrent protection response circuit 3: This circuit receives the overcurrent protection trigger signal, controls the output of the PWM pulse width modulation circuit to be turned off, and synchronously discharges and resets the PWM pulse width modulation slow start circuit 4, thereby turning off the output of the flyback high voltage power supply; PWM pulse width modulation slow start circuit 4: The PWM pulse width modulator COMP terminal is controlled by the overcurrent protection response circuit 3 and the PWM pulse width modulation slow start circuit 4, so that the multi-channel output flyback high-voltage power supply can complete the soft start of the power supply after the output overcurrent protection occurs in any output branch, and the multi-channel output flyback high-voltage power supply can restore the output state before the overcurrent.

[0029] Based on the above embodiments, the working mechanism of the output overcurrent multi-threshold protection restart circuit of the multi-output flyback high voltage power supply of the present invention is as follows: Multi-channel output current acquisition circuit 1: Figure 2 As shown, the multi-channel output current acquisition circuit 1 is composed of n channels of output current acquisition circuits 1 with the same structure. Now, taking the first channel of output current acquisition circuit 1 as an example, its working principle is explained.

[0030] The first output current acquisition circuit 1 is composed of a current sensor 1 and its peripheral circuits, and an IV signal conversion resistor R1, wherein one end of the IV signal conversion resistor R1 is connected to the sampling output end of the current sensor 1, and the other end is connected to the power supply ground of the subsequent output overcurrent trigger circuit 2.

[0031] The current sensor 1 converts the output current signal of the first output branch of the multi-output flyback high-voltage power supply into a sampling current signal in proportion by means of isolated collection. The sampling current signal flows through the IV signal conversion resistor R1, is converted into a voltage signal, and is transmitted to the next level circuit. By adjusting the resistance value of the IV signal conversion resistor R1, the size of the output current sampling voltage signal of the first output branch can be adjusted.

[0032] Multiple output overcurrent trigger circuit 2: Figure 2 As shown, the multi-channel output over-current trigger circuit 2 is composed of n channels of output over-current trigger circuits 2 with the same structure. Now, taking the first channel of output over-current trigger circuit 2 as an example, its working principle is explained.

[0033] The first output overcurrent trigger circuit 2 is composed of a comparator N1 and its peripheral circuits, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C1, a voltage-stabilizing diode V1 and an output combining diode V2.

[0034] Among them, one end of the resistor R2 is connected to the sampling output end of the current sensor 1, and the other end is connected to the non-inverting end of the comparator N1; one end of the capacitor C1 is connected to the non-inverting end of the comparator N1, and the other end is connected to the power supply ground of the comparator N1; one end of the resistor R5 is connected to the power supply high level Vcc of the comparator N1, and the other end is connected to the cathode of the Zener diode V1; one end of the resistor R3 is connected to the cathode of the Zener diode V1, and the other end is connected to the inverting end of the comparator N1; one end of the resistor R4 is connected to the inverting end of the comparator N1, and the other end is connected to the anode of the Zener diode V1. The anode of the output combining diode V2 is connected to the output end of the comparator N1, and the cathode of the output combining diode V2 is connected to the cathode of the output combining diode of the other output overcurrent trigger circuit 2, and then connected to the base of the transistor Q2 of the overcurrent protection response circuit 3.

[0035] The voltage-stabilizing diode V1 works in the reverse breakdown state. By adjusting the resistance ratio of the resistor R3 and the resistor R4, the voltage at the inverting terminal of the comparator N1, that is, the overcurrent protection trigger voltage of the first output branch, is adjusted; the resistor R5 is the current-limiting resistor when the voltage-stabilizing diode V1 is reversely broken down, to avoid overcurrent damage to V1; the resistor R2 and the capacitor C1 form an RC voltage integration circuit, and the trigger time is adjusted by adjusting the size of R2 and C1; the resistor R6 is the power supply current-limiting protection resistor of the comparator N1; the resistor R7 is the output pull-up resistor of the comparator N1.

[0036] When the output voltage of the current acquisition circuit 1 at the front stage is greater than the trigger voltage, the comparator N1 outputs a high level, the diode V2 is turned on, and current is injected into the base of the transistor Q2 of the back stage overcurrent protection response circuit 3, driving the transistor Q2 to turn on. At this time, the pull-up resistor R7 of the comparator N1 has the functions of power supply and current limiting, limiting the magnitude of the output current of the comparator N1, and protecting the back stage devices. The cathodes of the output combining diodes of the output overcurrent protection circuits of each output branch are connected in common. After any output branch output overcurrent protection circuit is triggered, it can output a high level, driving the transistor Q2 of the back stage overcurrent protection response circuit 3 to turn on. At this time, the output combining diodes of the output overcurrent protection circuits of other output branches are reversely cut off.

[0037] Overcurrent protection response circuit 3: Figure 2 As shown, the overcurrent protection response circuit 3 is composed of an anti-interference capacitor C2, a resistor R8, an NPN transistor Q2 and a current limiting resistor R9, and the NPN transistor Q2 is a protection trigger response transistor.

[0038] Among them, the base of the transistor Q2 is connected to the cathode of the output combining diode of each output branch output overcurrent protection circuit; after the anti-interference capacitor C2 is connected in parallel with the resistor R8, one end is connected to the base of the transistor Q2, and the other end is connected to the emitter of the transistor Q2, that is, the power supply ground of the comparator of the output overcurrent trigger circuit 2, which is also the power supply ground of the PWM pulse width modulator; one end of the current limiting resistor R9 is connected to the COMP end of the PWM controller in the PWM pulse width modulation slow start circuit 4, and the other end is connected to the collector of the transistor Q2.

[0039] The function of the anti-interference capacitor C2 is to filter out high-frequency interference signals to avoid false protection actions caused by interference signals. Therefore, its capacitance should not be too large, generally not more than 10nF, to avoid affecting the protection response time. The current limiting resistor R9 limits the size of the transient current when the transistor Q2 is turned on to avoid overcurrent in the transistor.

[0040] When an output branch of the power supply is triggered by overcurrent, transistor Q2 receives the drive signal and turns on, the voltage at the COMP terminal of the PWM controller changes from a high level to a low level, the diode V3 turns on, the capacitor C4 discharges, the PWM controller has no output, and the flyback power supply is turned off; when the drive signal disappears, the transistor Q2 is turned off, the PWM controller starts slowly, and the power supply returns to the output state before the overcurrent.

[0041] PWM pulse width modulation slow start circuit 4: Figure 2 As shown, the PWM pulse width modulation slow start circuit 4 is composed of a PNP transistor Q1, a diode V3, a diode V4, a resistor R10, a resistor R11, a resistor R12, a capacitor C3, a capacitor C4, a PWM pulse width modulator and its peripheral circuits.

[0042] Among them, one end of the resistor R11 is connected to the cathode of the diode V4, and the other end is connected to the Vref end of the PWM pulse width modulator; the anode of the diode V4 is connected to the common end of the capacitor C4 and the resistor R10; one end of the resistor R12 is connected to the Vref end of the PWM pulse width modulator, and the other end is connected to the anode of the diode V4; one end of the capacitor C4 is connected to the anode of the diode V4, and the other end is connected to the power supply ground of the PWM pulse width modulator; one end of the resistor R10 is connected to the anode of the diode V4, and the other end is connected to the base of the transistor Q1; the capacitor C3 is connected in parallel with the diode V3, the cathode of the diode V3 is connected to the COMP end of the PWM pulse width modulator, and the anode of the diode V3 is connected to the base of the transistor Q1; the emitter of the transistor Q1 is connected to the COMP end of the PWM pulse width modulator, and the collector of the transistor Q1 is connected to the power supply ground of the PWM pulse width modulator.

[0043] When the power supply starts or the overcurrent protection is triggered, the voltages at the COMP terminal and capacitor C4 terminal of the PWM pulse width modulator are 0 or less than the normal working voltage, the Vref terminal charges the capacitor C4 through the resistor R12, the transistor Q1 is turned on, the COMP terminal is slowly powered up to the normal working voltage, and the power supply starts slowly. Under steady-state working conditions, the voltage difference between the Vref terminal and the COMP terminal is applied to the resistors R12 and R10, and the diode V3 is turned on to avoid large reverse voltages at the b and e poles of the transistor; when the power supply is turned off, that is, when the PWM pulse width modulator is powered off, the capacitor C4 is quickly discharged to the Vref terminal through the diode V4 and the resistor R11, and the resistance value of the resistor R11 is much smaller than that of the resistor R12. The slow start time of the power supply can be adjusted by adjusting the parameters of C4, R12, and R10.

[0044] In summary, the present invention can perform overcurrent protection response for the multi-channel output flyback high-voltage power supply when any output branch outputs a current above the set threshold, and can perform multi-threshold adaptive response for the output overcurrent of each output branch, and can perform power supply shutdown and restart adjustment, thereby avoiding the problem that the multi-channel output flyback high-voltage power supply cannot be effectively protected when any output branch has an overcurrent, and the components are damaged by overcurrent stress, and at the same time avoids the problem that the output voltage of each output branch drops for a long time after the overcurrent protection, and the active devices on the load side of the output rear stage are linearly burned. The application of the present invention improves the working reliability of the multi-channel output flyback high-voltage power supply under complex working conditions, ensures the safety of the rear-stage electrical equipment, and at the same time improves the overall reliability and safety of the working system, making the multi-channel output flyback high-voltage power supply more competitive in the market, and having high practical value and economic value.

[0045] In addition, the application of the present invention does not conflict with the conventional primary PWM controller CS end overcurrent protection of the flyback power supply. When the present invention is adopted, the primary PWM controller CS end overcurrent protection can be adopted at the same time, thereby realizing dual overcurrent protection of the primary and secondary sides of the power supply, and further improving the reliability of the power supply.

[0046] Based on the above circuit, the present invention also discloses a working method of an output overcurrent protection circuit based on a multi-channel output flyback high voltage power supply, see Figure 3 , including the following steps: S1. The current signal of each branch of the flyback high-voltage power supply is collected in real time through the output current collection circuit 1, the current signal is converted into a voltage signal, and the voltage signal is sent to the output overcurrent trigger circuit 2, which provides basic data for subsequent judgment and triggering; S2. If an output overcurrent occurs in any output branch of the flyback high-voltage power supply, and the voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit 2 of the branch and lasts for a set time, the output overcurrent trigger circuit 2 of the corresponding branch outputs an overcurrent protection trigger signal, and sends the overcurrent protection trigger signal to the overcurrent protection response circuit 3. Each branch has an independent overcurrent trigger circuit, which realizes independent monitoring and protection of each branch and avoids local faults affecting the overall situation; S3. The overcurrent protection response circuit 3 controls the output of the PWM pulse width modulation circuit to shut down according to the overcurrent protection trigger signal, thereby shutting down the output of the flyback high-voltage power supply to prevent the overcurrent condition from further deteriorating, and synchronously discharges and resets the PWM pulse width modulation slow start circuit 4 to prepare for the subsequent soft start, thereby achieving comprehensive protection for the entire flyback high-voltage power supply and ensuring the safety of the power supply and the load; S4. After the flyback high-voltage power supply completes the output overcurrent protection, the flyback high-voltage power supply is soft-started through the PWM pulse width modulation slow start circuit 4, and the flyback high-voltage power supply is restored to the output state before the overcurrent. The soft start is realized by the PWM pulse width modulation slow start circuit, which avoids the impact and overcurrent problems that may be caused by direct start. The soft start process restores the power supply output to the state before the overcurrent, ensuring the stability and reliability of the power supply.

[0047] Embodiment three: See also Figure 3 This embodiment discloses a working method of an output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply, comprising the following steps: S1. The current signal of each branch of the flyback high-voltage power supply is collected in real time through the output current collection circuit 1, the current signal is converted into a voltage signal, and the voltage signal is sent to the output overcurrent trigger circuit 2, as follows: The current signal of each branch of the flyback high-voltage power supply is collected in real time by a current sensor; The current signal is converted into a voltage signal through the IV signal conversion resistor, and the voltage signal is sent to the output overcurrent trigger circuit 2.

[0048] S2. If an output overcurrent occurs in any output branch of the flyback high-voltage power supply, and the voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit 2 of the branch and lasts for a set time, the output overcurrent trigger circuit 2 of the corresponding branch outputs an overcurrent protection trigger signal, and sends the overcurrent protection trigger signal to the overcurrent protection response circuit 3, as follows: If an output overcurrent occurs in any output branch of the flyback high-voltage power supply, the voltage signal reaches the protection threshold voltage of the comparator of the branch and lasts for a set time, then the comparator N1 outputs a high level, the diode V2 is turned on, and current is injected into the base of the transistor Q2 of the subsequent overcurrent protection response circuit 3.

[0049] S3. The overcurrent protection response circuit 3 controls the output of the PWM pulse width modulation circuit to shut down according to the overcurrent protection trigger signal, thereby shutting down the output of the flyback high-voltage power supply, and synchronously discharging and resetting the PWM pulse width modulation slow start circuit 4; S4. After the flyback high-voltage power supply completes the output over-current protection, the flyback high-voltage power supply is soft-started through the PWM pulse width modulation slow-start circuit 4, and the flyback high-voltage power supply recovers the output state before the over-current.

[0050] In summary, the present invention aims at the problems existing in the current general multi-channel output flyback high-voltage power supply output overcurrent protection circuit, and faces the different overcurrent protection requirements of each output branch of the multi-channel output flyback high-voltage power supply. The present invention proposes an output overcurrent multi-threshold adaptive protection restart circuit based on the multi-channel output flyback high-voltage power supply. The circuit is composed of several functional circuits such as a multi-channel output current acquisition circuit 1, a multi-channel output overcurrent trigger circuit 2, an overcurrent protection response circuit 3, and a PWM pulse width modulation slow start circuit 4. It can respond to the overcurrent protection of the multi-channel output flyback high-voltage power supply when the current output exceeds the set threshold in any output branch. The response time can be matched and set according to the overcurrent protection requirements of the branch. Each output branch outputs an overcurrent multi-threshold adaptive response, and performs power supply shutdown and restart adjustment, thereby avoiding the problem that the multi-channel output flyback high-voltage power supply cannot be effectively protected when an overcurrent occurs in any output branch, and the components are damaged by overcurrent stress, and at the same time, the output voltage of each output branch drops for a long time after the overcurrent protection, and the active devices on the load side of the output back stage are linearly burned. The use of this circuit can improve the working reliability of the multi-channel output flyback high-voltage power supply under complex working conditions, ensure the safety of the subsequent electrical equipment, and improve the overall reliability and safety of the working system.

[0051] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An output overcurrent protection circuit based on a multi-channel output flyback high voltage power supply, characterized in that: The invention comprises a plurality of output current acquisition circuits (1) and a plurality of output overcurrent trigger circuits (2), each of the output current acquisition circuits (1) being connected to an output overcurrent trigger circuit (2), and the plurality of output overcurrent trigger circuits (2) being connected to a PWM pulse width modulation slow start circuit (4) via the same overcurrent protection response circuit (3).

2. The output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply according to claim 1, characterized in that: The output current acquisition circuit (1) comprises a current sensor, the current sensor is connected to an IV signal conversion unit, and the IV signal conversion unit is connected to an output overcurrent trigger circuit (2).

3. The output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply according to claim 2, characterized in that: The IV signal conversion unit comprises an IV signal conversion resistor, one end of which is respectively connected to the output overcurrent trigger circuit (2), the current sensor and the output current sampling signal interface, and the other end of which is grounded.

4. The output overcurrent protection circuit based on a multi-output flyback high-voltage power supply according to claim 1 or 2, characterized in that: The output overcurrent trigger circuit (2) comprises a comparator; The non-inverting terminal of the comparator is connected to the output current acquisition circuit (1) through an RC voltage integration circuit; The non-inverting end of the comparator is connected to the output current acquisition circuit (1) through the resistor R2, and the non-inverting end of the comparator is grounded through the capacitor C1; The inverting end of the comparator is connected to the power supply high level Vcc through the resistor R3 and the resistor R5 in sequence, the inverting end of the comparator and the resistor R3 are connected to the anode of the voltage-regulating diode V1 through the resistor R4, the cathode of the voltage-regulating diode V1 is connected between the resistor R3 and the resistor R5, the anode of the voltage-regulating diode V1 is grounded, the power supply input end of the comparator is connected to the power supply high level Vcc through the resistor R6, the power supply input end of the comparator is connected to the output end of the comparator through the resistor R7, the output end of the comparator is connected to the anode of the output combining diode V2, and the cathode of the output combining diode V2 is connected to the overcurrent protection response circuit (3).

5. The output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply according to claim 4, characterized in that: The RC voltage integration circuit comprises a resistor R2, one end of the resistor R2 is connected to the in-phase end of the comparator, the other end of the resistor R2 is connected to the output current acquisition circuit (1), and the in-phase end of the comparator and the resistor R2 are grounded via a capacitor C1.

6. The output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply according to claim 1, characterized in that: The overcurrent protection response circuit (3) comprises a transistor Q2, the base of the transistor Q2 is connected to the output overcurrent trigger circuit (2), the base of the transistor Q2 is connected to the emitter of the transistor Q2 via a resistor R8 and an anti-interference capacitor C2 respectively, the emitter of the transistor Q2 is grounded, and the collector of the transistor Q2 is connected to the PWM pulse width modulation slow start circuit (4) via a current limiting resistor R9.

7. The output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply according to claim 1 or 6, characterized in that: The PWM pulse width modulation slow start circuit (4) comprises a transistor Q1, the collector of the transistor Q1 is connected to the base of the transistor Q1 through a capacitor C4 and a resistor R10 in sequence, the collector of the transistor Q1 and the capacitor C4 are grounded, the emitter of the transistor Q1 is connected to each other through the COMP end of the PWM pulse width modulator, the cathode of the diode V3 and the capacitor C3 respectively, the other end of the capacitor C3 and the anode of the diode V3 are both connected to the base of the transistor Q1, the Vref end of the PWM pulse width modulator is connected between the capacitor C4 and the resistor R10 through a resistor R12, the Vref end of the PWM pulse width modulator is connected to the cathode of the diode V4 through a resistor R11, and the anode of the diode V4 is connected between the capacitor C4 and the resistor R10.

8. The working method of the output overcurrent protection circuit based on a multi-channel output flyback high-voltage power supply according to any one of claims 1 to 7, characterized in that: The following steps are involved: The output current acquisition circuit (1) acquires the current signal of each branch of the flyback high-voltage power supply in real time, converts the current signal into a voltage signal, and sends the voltage signal to the output overcurrent trigger circuit (2); If an output overcurrent occurs in any output branch of the flyback high-voltage power supply, after the voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit (2) of the branch and lasts for a set time, the output overcurrent trigger circuit (2) of the corresponding branch outputs an overcurrent protection trigger signal, and sends the overcurrent protection trigger signal to the overcurrent protection response circuit (3); The overcurrent protection response circuit (3) controls the output of the PWM pulse width modulation circuit to be turned off according to the overcurrent protection trigger signal, thereby turning off the output of the flyback high-voltage power supply, and synchronously discharging and resetting the PWM pulse width modulation slow start circuit (4); After the flyback high-voltage power supply completes the output over-current protection, the flyback high-voltage power supply is soft-started through the PWM pulse width modulation slow start circuit (4), and the flyback high-voltage power supply recovers the output state before the over-current.

9. The working method of the output overcurrent protection circuit based on the multi-channel output flyback high-voltage power supply according to claim 8, characterized in that: The steps of collecting the current signals of each branch of the flyback high-voltage power supply in real time through the output current collection circuit (1), converting the current signals into voltage signals, and sending the voltage signals to the output overcurrent trigger circuit (2) are specifically as follows: The current signal of each branch of the flyback high-voltage power supply is collected in real time by a current sensor; The current signal is converted into a voltage signal through an IV signal conversion resistor, and the voltage signal is sent to the output overcurrent trigger circuit (2).

10. The working method of the output overcurrent protection circuit based on the multi-channel output flyback high-voltage power supply according to claim 8, characterized in that: The steps of: if an output overcurrent occurs in any output branch of the flyback high-voltage power supply, and the voltage signal reaches the protection threshold voltage of the output overcurrent trigger circuit (2) of the branch and lasts for a set time, the output overcurrent trigger circuit (2) of the corresponding branch outputs an overcurrent protection trigger signal, and sends the overcurrent protection trigger signal to the overcurrent protection response circuit (3) are as follows: If an output overcurrent occurs in any output branch of the flyback high-voltage power supply, the voltage signal reaches the protection threshold voltage of the comparator of the branch and lasts for a set time, then the comparator N1 outputs a high level, the diode V2 is turned on, and current is injected into the base of the transistor Q2 of the subsequent overcurrent protection response circuit (3).

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