WO2023087716A1

WO2023087716A1 - Self-powered method for current detection of built-in high-voltage power tube

Info

Publication number: WO2023087716A1
Application number: PCT/CN2022/101740
Authority: WO
Inventors: 程兆辉; 于玮; 杜延滨; 杨昕禾
Original assignee: 东科半导体(安徽)股份有限公司
Priority date: 2021-11-16
Filing date: 2022-06-28
Publication date: 2023-05-25
Also published as: CN114050711A; CN114050711B

Abstract

Provided is a self-powered method for current detection of a built-in high-voltage power tube. A switching circuit based on a switching power supply comprises a transformer, a control chip, a power storage capacitor, a secondary rectifier diode, a secondary energy storage capacitor, and a load. The control chip internally comprises a high-voltage power tube, a low-voltage power tube, a self-powered diode, and a control circuit. Regulation and switching of a non-self-power supply period and a self-power supply period are achieved by means of on and off control over the high-voltage power tube and the low-voltage power tube of the control chip, such that the power tubes are turned off in each switching period when the excitation inductive current on the primary side of the transformer reaches the maximum excitation peak current of the internally set high-voltage power tube, and meanwhile, the requirements of maximum output power consistency and self-power supply are met.

Description

A self-power supply method with built-in high-voltage power tube current detection

This application claims the priority of the Chinese patent application with the application number 202111358529.7 and the title of the invention "a self-power supply method with built-in high-voltage power tube current detection" submitted to the China Patent Office on November 16, 2021.

technical field

The invention relates to the technical field of power supply technology, in particular to a self-power supply method with built-in high-voltage power tube current detection.

Background technique

The switching power supply self-power supply technology is that the control chip uses part of the energy of the transformer excitation inductance to supplement power supply to the control chip during the conduction stage of the high-voltage power switch tube. The switching power supply using self-powered technology can omit the auxiliary power supply winding of the traditional switching power supply without losing the conversion efficiency of the switching power supply. The schematic diagram of the existing switching power supply self-power supply technology is shown in Fig. 1 . The figure takes a flyback switching power supply as an example, which consists of a transformer T1, a control chip, a current detection resistor Rcs, a VCC power storage capacitor C1, a secondary rectifier diode D2, a secondary energy storage capacitor C2 and a load RL. Lm is the excitation inductance on the primary side of the transformer, Vin is the input voltage, Vout is the output voltage, Ilm is the excitation inductance current on the primary side of the transformer, and Iout is the output current. The control chip is composed of a high-voltage power tube Q1, a low-voltage power tube M1, a self-powered diode D1, and a control circuit. FB is the output voltage feedback signal, which can be the primary side feedback signal without optocoupler or the secondary side feedback signal with optocoupler, which is sent to the chip, and the control circuit generates signal OB according to FB and the detected Ilm current signal It is used to control the turn-on and turn-off of Q1, and generates a signal GT to control the turn-on and turn-off of M1. When Q1 and M1 are turned on at the same time, the control circuit is powered by C1, Ilm increases linearly, and the current on M1 Ilm1=Ilm; when Q1 is turned on and M1 is turned off, the self-power supply is turned on, and the OE terminal supplies power to the external capacitor through diode D1 C1 charges and makes C1 store energy, and provides power to the control circuit. At this time, the Ilm current continues to increase linearly, and the current Ilm2=Ilm flowing through the diode D1, and Ilm no longer flows through M1; when both Q1 and M1 are turned off, the Ilm current Start to transmit energy to the secondary, at this time the control circuit is powered by C1.

In the application where the maximum input power is fixed, the control chip can internally set the maximum excitation peak current of the high-voltage power tube according to the maximum input power. During the conduction period of the power tube Q1, no matter it is a self-supply cycle or a non-self-supply cycle, the current can pass The sampling resistor Rcs directly measures the excitation current to ensure the consistency of the maximum power; however, there is always energy consumption on the Rcs resistor, and its power consumption is reactive power, which affects the overall efficiency of the switching power supply, and the control chip needs an external CS pin. Increased hardware costs.

Contents of the invention

The technical problem solved by the present invention is to provide a self-power supply method with built-in high-voltage power tube current detection, which solves the problems of reactive power loss in switching power supplies in the prior art, and difficulty in achieving maximum output power consistency and self-power supply.

In order to solve the technical problem of the present invention, a self-power supply method with built-in high-voltage power tube current detection is provided, based on a switching power supply, including a transformer, a control chip, a power storage capacitor, a secondary rectifier diode, a secondary energy storage capacitor and a load , the excitation inductance on the primary side of the transformer is electrically connected to the control terminal of the control chip, the power supply terminal of the control chip is electrically connected to the power storage capacitor and then grounded, the ground terminal of the control chip is grounded, and the inside of the control chip includes high-voltage power tube, low-voltage power tube, self-powered diode and control circuit; when the high-voltage power tube and low-voltage power tube of the control chip are turned on at the same time, the control circuit is powered by the power storage capacitor, and the current flowing through the excitation inductance is Linear increase, the current flowing through the low-voltage power tube is equal to the current of the excitation inductance, the control circuit detects the gate and drain voltages of the low-voltage power tube through the internal current detection module, and obtains the current flowing through the low-voltage power tube; The high-voltage power tube of the control chip is turned on, and when the low-voltage power tube is turned off, the self-power supply is turned on, and the drain of the low-voltage power tube charges the power storage capacitor through the self-supply diode, and supplies power to the control circuit. The current of the excitation inductance continues to increase linearly. When the current flowing through the self-powered diode is equal to the current flowing through the excitation inductance, the current no longer flows through the low-voltage power tube, and the control circuit cannot directly measure the current flowing through the low-voltage power tube. The current value of the tube; when the high-voltage power tube and the low-voltage power tube of the control chip are turned off at the same time, the current flowing through the exciting inductor starts to transmit energy to the secondary, and the control circuit is powered by the power storage capacitor at this time.

Preferably, when the high-voltage power tube is turned on, the control circuit detects the VCC voltage of the power supply terminal of the control chip. When the VCC voltage is greater than or equal to the set voltage reference value Vcc_ref, it is judged that this cycle is a non-self-supply cycle. During the conduction period, the low-voltage power tube is always on, and the timer is started. When it is detected that the current flowing through the low-voltage power tube is greater than or equal to the maximum set current value Ipk, the high-voltage power tube and the low-voltage power tube are turned off at the same time, and this The hour timer value Ton is saved as a reference value Ton_ref=Ton.

Preferably, when the high-voltage power tube is turned on, the control circuit detects the VCC voltage of the power supply terminal of the control chip, and when the VCC voltage is less than the set voltage reference value Vcc_ref, it is judged that this cycle is a self-power supply cycle, and the low-voltage power tube is turned on at the same time, and Start the timer. When the current timing value of the timer is Ton=Ton1=Ton_ref×K, where 0<K<1, K is the internally set self-power supply proportional coefficient, and the K value is dynamically adjusted according to the self-power supply requirement. The timer is turned off in advance, and the timer continues to count. When the current value of the timer is equal to the reference value, that is, when Ton=Ton_ref, the high-voltage power tube is turned off.

Preferably, if it is detected that the number N of consecutive self-power supply cycles reaches the maximum value Nmax, that is, N=Nmax, then the next switching cycle is forced to be a non-self-power supply cycle.

Preferably, if after N=Nmax, the VCC voltage still cannot be maintained at Vcc_ref, and VCC continues to drop, then it is necessary to reduce the K value and increase the self-power supply time; if N<Nmax, VCC is detected at the turn-on moment of the next cycle ≥Vcc_ref, this cycle is a non-self-powered cycle.

Preferably, when the switching cycle count reaches the set reference value M, if the number of self-power supply cycles ≥ M×Nmax/(Nmax+1) indicates that the self-power supply is insufficient, then reduce the K value and increase the self-power supply time; if When the number of self-power supply cycles <M×(Nmax×0.7)/(Nmax+1), it means that the self-power supply cycle is longer, so increase the value of K; under other conditions, the value of K remains unchanged.

The technical effect of the present invention is: the present invention relates to a self-supply power supply method with a built-in high-voltage power tube current detection, based on a switching power supply switching circuit, including a transformer, a control chip, a power storage capacitor, a secondary rectifier diode, and a secondary energy storage capacitor and load, the primary side of the transformer is provided with an excitation inductance, and the control chip includes a high-voltage power tube, a low-voltage power tube, a self-powered diode and a control circuit; through the on-off control of the high-voltage power tube and low-voltage power tube of the control chip , to realize the regulation and switching of the non-self-supply cycle and the self-supply cycle, so that each switching cycle turns off the power tube when the excitation inductance current on the primary side of the transformer reaches the internally set maximum excitation peak current of the high-voltage power tube, and at the same time, the maximum output power is consistent and self-powered requirements.

Description of drawings

Fig. 1 is the circuit diagram of a switching power supply embodiment in the prior art;

Fig. 2 is a circuit diagram of a switching power supply embodiment in the present invention;

Fig. 3 is the flow chart of an embodiment of the self-supply method of built-in high-voltage power tube current detection of the present invention;

Fig. 4 is the flow chart of another embodiment of the self-supply method of built-in high-voltage power tube current detection of the present invention;

Fig. 5 is the circuit diagram of the control chip in another embodiment of the self-supply method of built-in high-voltage power tube current detection of the present invention;

FIG. 6 is a cycle timing diagram of another embodiment of the self-supply method with built-in high-voltage power tube current detection of the present invention.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described in more detail below in conjunction with the accompanying drawings and specific embodiments. Preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field of the present invention. Terms used in the description of the present invention are only for the purpose of describing specific embodiments, and are not used to limit the present invention. The term "and/or" used in this specification includes any and all combinations of one or more of the associated listed items.

Fig. 2 is an embodiment of a switching power supply circuit with built-in high-voltage power tube current detection with self-power supply technology. Figure 2 takes a flyback switching power supply as an example. The circuit includes a transformer T1, a control chip, a VCC power storage capacitor C1, a secondary rectifier diode D2, a secondary energy storage capacitor C2 and a load RL. Lm is the excitation inductance on the primary side of the transformer, Vin is the input voltage, Vout is the output voltage, Ilm is the excitation inductance current on the primary side of the transformer, and Iout is the output current. The ports included in the control chip include a feedback terminal FB, a power supply terminal VCC, a ground terminal PGND, and a control terminal OC. The control chip includes a high-voltage power tube Q1, a low-voltage power tube M1, a self-powered diode D1 and a control circuit.

Preferably, when Q1 and M1 are turned on at the same time, the control circuit is powered by C1, Ilm increases linearly, the current Ilm1=Ilm on M1, the control circuit detects the OE and GT voltages through the internal current detection module, according to the mirror current source principle The value of Ilm can be directly detected; when Q1 is turned on and M1 is turned off, the self-power supply is turned on, and the OE terminal charges the external capacitor C1 through the diode D1 to store energy in C1 and provide power to the control circuit. At this time, the Ilm current continues to be linear increase, the current Ilm2=Ilm flowing through diode D1, Ilm no longer flows through M1, so the control circuit cannot directly measure the value of Ilm; Power is provided by C1.

Preferably, as shown in Figure 2, when it is detected that the VCC voltage is less than the internally set reference value, the current Pwm cycle is defined as a self-powered cycle; when it is detected that the VCC voltage is greater than or equal to the internally set reference value, the current Pwm cycle is defined as is a non-self-powered cycle.

The key problem to be solved by the present invention is how to obtain an accurate current Ilm value during the self-supply cycle, that is, during the period when Q1 is turned on and M1 is turned off, so that the excitation inductance current on the primary side of the transformer reaches the internally set high-voltage power tube in each switching cycle. Turn off the power tube at the maximum excitation peak current, while meeting the requirements of maximum output power consistency and self-supply.

Preferably, the conduction time width of the high-voltage power tube obtained in the non-self-supply period can be used as the conduction width of the high-voltage power tube in the self-supply period, so as to ensure that the peak current of the non-self-supply period is the same as that of the self-supply period.

Preferably, an embodiment of a self-supply method with built-in high-voltage power tube current detection proposed by the present invention, the corresponding flow chart is shown in FIG. 3 .

Preferably, the VCC voltage is detected at the moment when the high-voltage power tube is turned on. When the VCC voltage is greater than or equal to the set value Vcc_ref, it is judged that this cycle is a non-self-powered cycle. During the conduction period of the high-voltage power tube, the low-voltage power tube is always on. And start the timer, when it is detected that Ilm1 is greater than or equal to the maximum set current Ipk, turn off the high and low voltage power tubes at the same time, and save the value Ton of the timer at this time as the reference value Ton_ref=Ton.

Preferably, the VCC voltage is detected at the moment when the high-voltage power tube is turned on. When the VCC voltage is less than the set value Vcc_ref, it is judged that this cycle is a self-supply cycle, and the low-voltage power tube is turned on at the same time, and the timer is started. When the timer Ton=Ton1 =Ton_ref×K (among them, 0<K<1, K is the self-supply proportional coefficient set internally, and the K value is dynamically adjusted according to the self-supply demand), the low-voltage power tube is turned off in advance, and the timer Ton continues to count. When the current value of the switch is equal to the reference value, that is, when Ton=Ton_ref, the high voltage power tube is turned off. According to Ipk=Vin×Ton_ref/Lm, when Vin is constant, the Ipk of the self-powered period and the non-self-powered period are the same. The input voltage Vin is obtained by rectifying the AC power of the city. If the continuous time of the self-power supply cycle is too long, the power frequency fluctuation of Vin will cause an error to the maximum peak current. Therefore, in order to eliminate the influence of Vin fluctuation on Ipk, the maximum continuous self-power supply cycle should be limited. The number N cannot be too much. Preferably, if it is detected that the number of consecutive self-power supply cycles reaches the maximum value, that is, N=Nmax, then the next switching cycle is forced to be a non-self-power supply cycle.

Preferably, if after N=Nmax, the VCC voltage is still unable to be maintained at Vcc_ref, if after N=Nmax, the VCC voltage is still unable to be maintained at Vcc_ref, and VCC continues to drop, then it is necessary to reduce the K value and increase the self-power supply time; if N<Nmax, VCC≥Vcc_ref is detected at the turn-on moment of the high-voltage power tube in the next cycle, and this cycle is a non-self-supply cycle; if the K value is too small, the self-supply time is too long, and the self-supply cycle accounts for all cycles when the system is stable. If the ratio is too small, the system efficiency will be reduced; in order to meet the efficiency requirements, it is necessary to increase the K value, reduce the duration of VCC self-power supply, and increase the proportion of self-power supply cycle to all cycles.

Further, as shown in Figure 4, for K value adjustment, in order to ensure system stability and anti-interference performance, the dynamic adjustment speed of K value should not be too fast, so it is necessary to use more when calculating the proportion of detection self-power supply cycle to all cycles The switching cycle is defined as the switching cycle setting reference value M, generally hundreds to thousands. When the switching cycle counts to the reference value M, if the number of self-power supply cycles ≥ M×Nmax/(Nmax+1), it means that the self-power supply is insufficient, and the value of K should be reduced; if the number of self-power supply cycles <M×(Nmax ×0.7)/(Nmax+1), it means that the self-power supply time is too long, and the K value should be increased; under other conditions, the K value remains unchanged.

Further, as shown in Figure 5, it shows the internal composition of the control chip in the present invention, which includes MOS transistors M2-M5, operational amplifier OP, and resistor Rs to form the detection circuit of the inductor current Ilm1, that is, the current Ilm1 is mirrored according to a certain ratio Zoom out, and the current value of Ilm1 can be known through the voltage Vcs of the Rs resistor. The reference peak current generator obtains the excitation inductor peak current Ipk required by the current system according to the voltage value of the external input FB, and then obtains the corresponding Vcs_ref according to the proportional relationship of the Ilm1 current detection circuit, and inputs it into the comparator cmp1. When Vcs>Vcs_ref, That is, when Ilm>Ipk, the output signal Ipk_ok is at high level. VBE is the voltage difference between OB and OE, Pwm is the digital signal that generates VBE, the comparator cmp2 compares VCC with the chip preset reference VCC voltage Vcc_ref, and uses the rising edge of Pwm to collect the output of cmp2 through the D flip-flop D-fifo Signal, whether the output of the D flip-flop and the number of consecutive cycles output by the continuous cycle counter Cnt2 are equal to the signal N_equ_Max of Nmax pass through the NOR gate to generate the signal Auto. When Auto is low, it means that this cycle does not need self-power supply. When it is detected When Ipk_ok is at a high level, turn off the high and low voltage power tubes at the same time. At this time, the high level time Ton_ref of Pwm is obtained through Timer1; when Auto is at a high level, it means that the cycle needs to be self-powered, and the K value is obtained by adjusting the module Cnt1 according to the K value , and then the Ton1_ref is generated by the multiplier, connected to Timer1, and the Ton1_ok signal for controlling the shutdown of the low-voltage power tube M1 and the Tonref_ok signal for controlling the shutdown of the high-voltage power tube Q1 are obtained. Select which signal to use to turn off the power tube according to Auto through the selectors Mux1 and Mux2, and then generate the Pwm signal for controlling the high-voltage power and the Gate signal for controlling the low-voltage power tube through the RS flip-flop, and finally generate a direct drive power tube through the driver The signals OB and GT.

Fig. 6 is the key signal waveform diagram of the above circuit diagram. It can be seen from Fig. 6 that Ilm1 is in the non-self-power supply cycle, and the high and low voltage tubes are turned on at the same time. Ilm1 and Ilm coincide, and the Ilm current can be measured through Vcs; the self-power supply cycle, In the stage when the high and low voltage tubes are turned on at the same time, Ilm1 and Ilm coincide. When the self-power supply operation starts, Ilm no longer flows through the M1 tube, and the Ilm current cannot be measured by Vcs. The current Ilm2=Ilm flowing through the diode D1. Figure 6 takes Nmax=4 as an example. The first Pwm cycle is a non-self-powered cycle, and the on-time is counted as Ton_ref; the rising edge of the second to fifth Pwm cycles does not detect VCC≥Vcc_ref, so they are all self-powered. In the power supply cycle, the conduction time of the high-voltage power transistor Q1 is forced to be Ton_ref, and the Gate signal will be turned off in advance at Ton1, and the self-power supply action will be turned on; although the rising edge of the sixth Pwm cycle does not detect VCC≥Vcc_ref, because Nmax has reached , so it is forced to be a non-self-power supply cycle; the 7th to 9th Pwm cycle is a self-power supply cycle; the rising edge of the 10th Pwm detects VCC≥Vcc_ref, so it is a non-self-power supply cycle. After continuously counting M Pwm cycles, the time of Ton1 can be changed according to the K value adjustment strategy, so as to change the self-power supply time to meet the system requirements.

It can be seen that the present invention relates to a self-power supply method with built-in high-voltage power tube current detection, based on a switching power supply switching circuit, including a transformer, a control chip, a power storage capacitor, a secondary rectifier diode, a secondary energy storage capacitor and a load, The control chip includes a high-voltage power tube, a low-voltage power tube, a self-powered diode and a control circuit; through the on-off control of the high-voltage power tube and low-voltage power tube of the control chip, the regulation of the non-self-powered cycle and the self-powered cycle is realized. And switching, so that each switching cycle turns off the power tube when the excitation inductance current on the primary side of the transformer reaches the maximum excitation peak current of the internally set high-voltage power tube, and at the same time meets the requirements of maximum output power consistency and self-power supply.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims

A self-power supply method with built-in high-voltage power tube current detection, characterized in that, based on a switching power supply, including a transformer, a control chip, a power storage capacitor, a secondary rectifier diode, a secondary energy storage capacitor and a load, the primary side of the transformer The excitation inductance is electrically connected to the control terminal of the control chip, the power supply terminal of the control chip is electrically connected to the power storage capacitor and then grounded, the ground terminal of the control chip is grounded, and the control chip includes a high-voltage power tube, a low-voltage power tube, Self-powered diodes and control circuitry;

When the high-voltage power tube and the low-voltage power tube of the control chip are turned on at the same time, the control circuit is powered by the power storage capacitor, the current flowing through the excitation inductor increases linearly, and the current flowing through the low-voltage power tube is equal to the The current of the excitation inductance, the control circuit detects the gate and drain voltages of the low-voltage power tube through the internal current detection module, and obtains the current flowing through the low-voltage power tube;

When the high-voltage power tube of the control chip is turned on and the low-voltage power tube is turned off, the self-power supply is turned on, and the drain of the low-voltage power tube charges the power storage capacitor through the self-supply diode, and supplies power to the control circuit. The current of the exciting inductor continues to increase linearly. When the current flowing through the self-powered diode is equal to the current flowing through the exciting inductor, the current no longer flows through the low-voltage power tube, and the control circuit cannot directly measure the current flowing through the low-voltage power tube. The current value of the power tube;

When the high-voltage power tube and the low-voltage power tube of the control chip are turned off at the same time, the current flowing through the excitation inductor starts to transmit energy to the secondary, and at this time the control circuit is powered by the power storage capacitor.
The self-supply method of built-in high-voltage power tube current detection according to claim 1, characterized in that, when the high-voltage power tube is turned on, the control circuit detects the VCC voltage of the power supply terminal of the control chip, and when the VCC voltage is greater than or equal to the set voltage When the reference value Vcc_ref is used, it is judged that this period is not a self-powered period. During the conduction period of the high-voltage power tube, the low-voltage power tube is always on, and the timer is started. When it is detected that the current flowing through the low-voltage power tube is greater than or equal to the maximum setting When the current value is Ipk, the high-voltage power tube and the low-voltage power tube are turned off simultaneously, and the timer value Ton at this time is saved as a reference value Ton_ref=Ton.
The self-supply method of built-in high-voltage power tube current detection according to claim 2 is characterized in that, when the high-voltage power tube is turned on, the control circuit detects the VCC voltage of the power supply terminal of the control chip, and when the VCC voltage is less than the set voltage reference value When Vcc_ref, it is judged that this cycle is a self-power supply cycle, the low-voltage power tube is turned on at the same time, and the timer is started. When the current timing value of the timer is Ton=Ton1=Ton_ref×K, where 0<K<1, K is the internal setting Set the self-power supply proportional coefficient, K value is dynamically adjusted according to the self-power supply demand, the low-voltage power tube is turned off in advance, and the timer continues to count. When the current value of the timer is equal to the reference value, that is, Ton=Ton_ref, the high-voltage power tube is turned off .
The self-supply method of the built-in high-voltage power tube current detection according to claim 3 is characterized in that, if it is detected that the continuous number N of self-supply cycles reaches the maximum value Nmax, that is, N=Nmax, then the next switching cycle is forced to be non-self-powered cycle.
The self-supply method of built-in high-voltage power tube current detection according to claim 4 is characterized in that, if after N=Nmax, still can't maintain VCC voltage at Vcc_ref, VCC continues to decline, just need to reduce K value this moment, increase Self-power supply time; if N<Nmax, VCC≥Vcc_ref is detected at the turn-on moment of the high-voltage power transistor in the next cycle, and this cycle is a non-self-power supply cycle.
The self-supply method for built-in high-voltage power tube current detection according to claim 5 is characterized in that, when the switching cycle count reaches the set reference value M, if the number of self-supply cycles ≥ M×Nmax/(Nmax+ 1), indicating that the self-power supply is insufficient, then reduce the K value and increase the self-power supply time; if the number of self-power supply cycles <M×(Nmax×0.7)/(Nmax+1), it means that the self-power supply time is longer, then Increase the K value; under other conditions, the K value remains unchanged.