CN103236790B - Method and device for controlling half-hysteresis ring pulse sequences of switching power supply in continuous working mode - Google Patents

Abstract

The invention discloses a semi-hysteresis pulse sequence control method and its device for a switching power supply in a continuous working mode: at the beginning of each switching cycle, according to the difference between the output voltage V _o of the switching converter and the reference voltage V _ref The relationship selects the active control pulse for this switching period. The control pulse selection rule is: if V _o is lower than V _ref , the control pulse _PH is used to control the switching tube S in the switching converter; otherwise, if V _o is higher than V _ref , the switching tube S is controlled by the control pulse _PL . The high-level duration of each control pulse is a preset fixed value, and the low-level duration is obtained by comparing the inductor current _IL with a preset estimated current _IV . The method can be used to control high-power switching converters working in continuous mode. The control technology is simple and easy, the stability and anti-interference ability is strong, the dynamic performance is good, and it is suitable for switching converters of various topological structures.

Description

Semi-hysteretic loop pulse sequence control method and device for switching power supply in continuous operation mode

technical field

The invention relates to a switching power supply, in particular to a control method and device for a switching converter.

Background technique

A switching power supply is a power supply that maintains a stable output voltage by controlling the turn-on and turn-off time of the main power switch. It has the advantages of low power consumption, high power conversion efficiency, small size, wide voltage regulation range, etc., and is widely used in various electronic products. With the development of power electronics technology and the popularization of battery-powered portable electronic devices, the performance requirements of switching power supplies are getting higher and higher. In order to improve the shortcomings of traditional pulse width modulation (PWM) technology, such as slow transient response speed and difficult compensation network design, some new control methods have been proposed in recent years to improve the performance of switching power supply and make it meet the requirements of electronic equipment for switching. power requirements.

Pulse sequence (PT) control technology is a new fixed-frequency control method proposed for switching converters working in discontinuous current mode (DCM). adjustment. Since the pulse sequence control switching converter has the advantages of simple circuit implementation, no need for compensation network, fast transient response and strong robustness, it is very suitable for switching power supply control systems with high reliability requirements. However, when the pulse sequence control switching converter works in the inductor current continuous mode (CCM), since the pulse sequence controller indirectly adjusts the output voltage by adjusting the inductor current, the controller has hysteresis in the adjustment of the output voltage, resulting in the switching converter. Low-frequency fluctuation phenomenon, steady-state and transient performance deterioration. The current research shows that by increasing the equivalent series resistance (ESR) of the output filter capacitor, the low-frequency fluctuation phenomenon of the pulse sequence control continuous operation mode switching converter can be suppressed, but increasing the equivalent series resistance of the output filter capacitor will make the output voltage The ripple increases.

Contents of the invention

The purpose of the present invention is to provide a control method of a switching power supply, so as to overcome the technical shortcomings of the existing pulse sequence control working in the continuous mode of the inductor current. The method can be used to control high-power switching converters working in continuous mode. The control technology is simple and easy, the stability and anti-interference ability are strong, and the dynamic performance is good, and it is suitable for switching converters with various topological structures.

The present invention realizes its object of the invention, and the adopted technical scheme is: the semi-hysteresis loop pulse sequence control method of the continuous operation mode switching power supply, the semi-hysteresis loop pulse sequence regulation system of the continuous operation mode switching power supply composed of the converter TD and the controller, Its working method includes: at the beginning of each switching cycle, select the effective control pulse in the switching cycle according to the switching converter output voltage control pulse selection rules, so as to realize the control of the continuous working mode switching converter; the control pulse selection The rule is: if V _o is lower than V _ref , the switch tube S in the switching converter is controlled by the control pulse _PH ; otherwise, if V _o is higher than V _ref , the switch tube S is controlled by the control pulse _PL .

The method for generating the control pulse P _H mentioned above is: at the moment t ₀ at the beginning of a certain switching cycle, the one-shot timer starts counting, the control pulse P _H changes from low level to high level, and the switch in the converter TD The tube S is turned on, and the inductor current I _L rises; at the moment t ₀ +τ _{on_H} , the one-shot timer ends timing, the control pulse P _H becomes low level after keeping at a high level for a fixed time τ _{on_H} , and the switch tube S is turned off is off, the diode D is turned on, and the inductor current drops; when the inductor current drops to the preset inductor current valley value _Iv , the control pulse P _H changes to a high level after the low level time τ _{off_H} , and the one-shot timer Start timing again, switch tube S is turned on again, and the converter enters the next switching cycle.

The above method for generating the control pulse _PL is similar to the above process, the difference is that the duration of the control pulse _PL being at low level in one switching cycle is τ _{on_L} (τ _{on_L} <τ _{on_H} ).

Compared with prior art, the beneficial effect of the present invention is:

1. The present invention provides a simple and reliable control method for the continuous operation mode switching converter. The control method can complete the control of the main switching tube S in the converter by detecting the output voltage once at the beginning of each switching period and simply judging its magnitude, and detecting the inductor current and simply judging its magnitude. It overcomes the unavoidable shortcomings of the traditional continuous mode converter control method, such as complex detection and processing feedback, cumbersome design of compensation links, and the like.

2. The control method provided by the present invention can suppress the low-frequency fluctuation phenomenon of the pulse sequence control continuous operation mode switching converter, so that the working range of the controlled converter is not limited by the critical condition of the inductance current of the pulse sequence control converter, which broadens the application scope.

Another object of the present invention is to provide a device for implementing the above method for controlling a switching power supply.

The technical solution adopted by the present invention to realize the object of the invention is: a device for realizing the control method of the above switching power supply, which is composed of a converter and a controller, and the controller includes a voltage detection circuit, a current detection and comparison circuit, a pulse selector, Pulse generator, one-shot timer 1, one-shot timer 2, driving circuit, its structural characteristics are: current detection and comparison circuit is connected with pulse selector, pulse generator, one-shot timer 1, one-shot timer 2 ; The voltage detection circuit, the pulse selector, the pulse generator and the drive circuit are connected in sequence; the pulse generator is connected to the current detection and comparison circuit, the one-shot timer 1 and the one-shot timer 2 .

The working process and principle of the device are: the current detection and comparison circuit detects the inductor current _IL , and compares the inductor current _IL with the preset inductor current valley value _Iv , and when the inductor current _IL drops to the preset inductor current At the time of the valley I _v , the clock pulse signal V _C1 is generated; when the clock pulse comes, the pulse selector compares the relationship between the output voltage V _o and the reference voltage V _ref at this time, and outputs the logic signal representing the comparison result to the pulse generator The pulse generator generates control pulses P _H and P _L with different frequency and duty cycle according to the one-shot timer timing and the comparison result of the current detection and comparison circuit, and according to the output voltage V _o and the reference voltage V _ref Output the corresponding control pulse to control the switching tube S of the converter.

It can be seen that the above method of the present invention can be realized conveniently and reliably by using the above device.

The specific composition of the above current detection and comparison circuit is as follows: it is composed of the current detection circuit ID and the comparator AC1; the positive terminal of the comparator AC1 is connected to the preset valley current _Iv , and the negative terminal is connected to the inductance output by the current detection circuit ID current I _L .

In this way, the comparator AC1 compares the inductor current _IL with the preset valley current _Iv , and when the inductor current _IL is lower than the preset valley current _Iv , the output signal V _C1 of the comparator AC1 is at a high level, Conversely, when I _L is lower than I _v , V _C1 is low.

The specific composition of the above-mentioned pulse selector is as follows: it is composed of a comparator AC2 and a D flip-flop DFF; the positive terminal of the comparator AC2 is connected to the converter output voltage V _o output by the voltage detection circuit VD, and the negative terminal is connected to the reference voltage V _ref , the output terminal of AC2 is connected with the D terminal of the D flip-flop DFF.

In this way, the comparator AC2 compares the output voltage V _o with the reference voltage V _ref , when the output voltage V _o is lower than the reference voltage V _ref , the output signal V _C2 of the comparator AC2 is low level, otherwise, when V _{o is} low At V _ref , V _C2 is high level; when the rising edge of V _C1 comes, the D flip-flop DFF outputs the output signal V _C2 of the comparator AC2 to the Q terminal to generate a pulse selection signal V _Q , according to the flip-flop The working principle: V _Q remains unchanged until the next rising edge of V _C1 comes, and The level of the level is always opposite to V _Q.

The concrete composition of above-mentioned pulse generator is: be made up of RS flip-flop RSFF1, RSFF2, AND gate AG1, AG2, and OR gate OG; _C1 and R terminals are respectively connected to the output signals V _TL and V _TH of the one-shot timer OOT1 and OOT2; the input terminal of the AND gate AG1 is connected to the Q terminal of the RS flip-flop RSFF1 and the Q terminal of the flip-flop DFF, and the input terminal of the AND gate AG2 Connect to the Q terminal of the RS flip-flop RSFF2 and the flip-flop DFF terminal; the input terminal of the OR gate OG is connected to the output terminals of the AND gates AG1 and AG2, and the output terminal of OG1 is connected to the driving circuit DR of the switching tube S.

In this way, when the inductor current I _L drops to the preset inductor current valley value _Iv , the S terminal of the RS flip-flop RSFF1 inputs a high level, and the control pulse signal _PL output by RSFF1 is a high level, when the one-shot timer At the end of OOT1 timing, the R terminal of RS flip-flop RSFF1 inputs high level, and the control pulse signal _PL output by RSFF1 becomes low level; the working process of RS flip-flop RSFF2 is similar to the above RSFF1, but because the R terminal of RSFF2 Connect the one-shot timer OOT2, the time length of the one-shot timer OOT2 is longer than the time length of the one-shot timer OOT1, the high level duration of the control pulse signal P _H output by RSFF2 is greater than _PL ; when the pulse selection signal V _Q is high level, When it is low level, the AND gate AG1 is opened, AG2 is blocked, and the OR gate OG outputs the control pulse _PL to the drive circuit; on the contrary, when the pulse selection signal V _Q is low level, When it is high level, the AND gate AG2 is opened, AG1 is blocked, and the OR gate OG outputs the control pulse P _H to the drive circuit.

The above pulse selector and pulse generator have a simple structure and stable performance, and can reliably realize related functions in the method of the present invention. In the above control device, the selection and generation of the control pulses can also be realized by using existing circuits with other structures.

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

FIG. 1 is a signal flow chart of a method according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram of the circuit structure of Embodiment 1 of the present invention.

FIG. 3 is a circuit structure diagram of a current detection and comparison circuit according to Embodiment 1 of the present invention.

FIG. 4 is a circuit structure diagram of a pulse picker according to Embodiment 1 of the present invention.

FIG. 5 is a circuit structure diagram of a pulse generator according to Embodiment 1 of the present invention.

FIG. 6a is a time-domain simulation waveform diagram of the inductor current I _L in a certain period of time under steady-state conditions according to Embodiment 1 of the present invention.

Fig. 6b is a time-domain simulation waveform diagram of the clock pulse signal V _C1 at the beginning of the switching period generated by the current detection and comparison circuit in the same period as Fig. 6a.

Fig. 6c is a time-domain simulation waveform diagram of the control pulse signal P _H at the same period as Fig. 6a.

Fig. 6d is a time-domain simulation waveform diagram of the control pulse signal _PL in the same period as Fig. 6a.

Fig. 6e is a time-domain simulation waveform diagram of the effective control pulse signal _VP at the same time period as Fig. 6a.

Fig. 6f is a time-domain simulation waveform diagram of the output voltage V _o of the converter in the same period as Fig. 6a.

The simulation conditions in Figure 6 are as follows: input voltage V _in =50V, output reference voltage V _ref =20V, inductance L=400μH, capacitance C=200μF, load resistance R=10Ω, and the duration of the high level of the control pulse P _H is τ _{on_H} =8 μs, the duration of the high level of the control pulse _PL is τ _{on_L} =1 μs, and the preset valley current I _v =1.8A.

Fig. 7a is a time-domain simulation waveform diagram of the effective control of the P _H pulse in the pulse signal in a certain period of time under the steady-state condition of the conventional pulse sequence control converter.

Fig. 7b is a time-domain simulation waveform diagram of the effective control of the P _L pulse in the pulse signal during the same period as Fig. 7a in the conventional pulse sequence control converter.

Fig. 7c is a time-domain simulation waveform diagram of the output voltage V _o of the converter in the same period as Fig. 7a in the conventional pulse sequence control converter.

The simulation conditions in Figure 7 are as follows: input voltage V _in =50V, output reference voltage V _ref =20V, inductance L=400μH, capacitance C=200μF, load resistance R=10Ω, and the duty cycle of the control pulse P _H is D _H = 0.8. The duty cycle of the control pulse _PL is D _L =0.1, and the switching frequency of the converter is f=100kHz.

FIG. 8 is a block diagram of the circuit structure of Embodiment 2 of the present invention.

FIG. 9 is a block diagram of the circuit structure of Embodiment 3 of the present invention.

Detailed ways

Embodiment one

Fig. 1 shows, a kind of embodiment of the present invention is, a kind of control method of switching power supply, and its specific practice is:

At the beginning of each switching period, the controller selects an effective control pulse in the switching period according to the relationship between the output voltage V _o of the switching converter TD and the reference voltage V _ref , so as to realize the control of the switching converter TD. The control pulse selection rule is: if V _o is lower than V _ref , the control pulse _PH is used to control the switching tube S in the switching converter; otherwise, if V _o is higher than V _ref , the switching tube S is controlled by the control pulse _PL .

The method for the controller to generate the control pulse P _H is: at the moment t ₀ at the beginning of a certain switching period, the one-shot timer starts counting, the control pulse P _H changes from low level to high level, and the switch in the converter TD The tube S is turned on, and the inductor current I _L rises; at the moment t ₀ +τ _{on_H} , the one-shot timer ends timing, the control pulse P _H becomes low level after keeping at a high level for a fixed time τ _{on_H} , and the switch tube S is turned off is off, the diode D is turned on, and the inductor current drops; when the inductor current drops to the preset valley current I _v , the control pulse P _H becomes high after the low level time τ _{off_H} , and the converter enters the next switching cycle.

The method for the controller to generate the control pulse _PL is similar to the above process, the difference is that the duration of the control pulse _PL being low level in one switching cycle is τ _{on_L} (τ _{on_L} <τ _{on_H} ).

This example adopts the following devices, which can realize the above-mentioned control method conveniently and quickly.

Fig. 2 shows that the device of the control method of the switching power supply in this example is composed of a converter TD and a controller, and the controller includes a voltage detection circuit VD, a current detection and comparison circuit IDC, a pulse selector PS, a pulse generator PG, One-shot timer OOT1, one-shot timer OOT2, drive circuit DR, its structural characteristics are: current detection and comparison circuit IDC is connected with pulse selector PS, pulse generator PG, one-shot timer OTT1, one-shot timer OTT2 The voltage detection circuit VD, the pulse selector PS, the pulse generator PG, and the driving circuit are connected to DR in sequence; the pulse generator PG is connected to the current detection and comparison circuit IDC, the one-shot timer OOT1, and the one-shot timer OOT2.

Figure 3 shows that the specific composition of the current detection and comparison circuit IDC in this example is as follows: it is composed of the current detection circuit ID and the comparator AC1; the positive terminal of the comparator AC1 is connected to the preset valley current _Iv , and the negative terminal is connected to The inductor current _IL output by the current detection circuit ID; the output terminal of the comparator AC1 is connected with the pulse selector PS, the pulse generator PG, the one-shot timer OTT1, and the one-shot timer OTT2.

Figure 4 shows that the specific composition of the pulse selector PS in this example is as follows: it is composed of a comparator AC2 and a D flip-flop DFF; the positive terminal of the comparator AC2 is connected to the converter output voltage V _o output by the voltage detection circuit VD, and the negative terminal The terminal is connected to the reference voltage V _ref , the output terminal of AC2 is connected to the D terminal of the D flip-flop DFF; the output terminals Q and Connected to the pulse generator PG.

Fig. 5 shows, the concrete composition of the pulse generator PG of this example is: by RS flip-flop RSFF1, RSFF2, AND gate AG1, AG2, and OR gate OG is formed; The output signal V _C1 of the AND comparison circuit, the R terminal is respectively connected to the output signals V _TL and V _TH of the one-shot timer OOT1 and OOT2; the input terminal of the AND gate AG1 is connected to the Q terminal of the RS flip-flop RSFF1 and the Q terminal of the flip-flop DFF , the input terminal of the AND gate AG2 is connected to the Q terminal of the RS flip-flop RSFF2 and the flip-flop DFF terminal; the input terminal of the OR gate OG is connected to the output terminals of the AND gates AG1 and AG2, and the output terminal of OG1 is connected to the driving circuit DR of the switching tube S.

Its work process and principle of the device of this example are:

Figure 1-5 shows that the current detection and comparison circuit IDC generates the clock pulse signal V _C1 at the beginning of the switch tube cycle; when the clock pulse signal V _C1 comes, the pulse selector PS compares the output voltage V _o with the reference voltage V _ref at this time The magnitude relationship, and output the logic signal representing the comparison result to the pulse generator PG; at the same time, the one-shot timer OOT1 or OOT2 starts timing; the pulse generator PG according to the timing signal V of the one-shot timer OOT1 or OOT2 _TL or V _TH , clock pulse signal V _C1 generate control pulses _PH and _PL with different frequencies and duty ratios to control the switch tube S of the converter.

The current detection and comparison circuit IDC completes the detection of the inductor current and compares the clock pulse signal V _C1 at the beginning of the switch cycle: Figures 2 and 3 show that the current detection circuit ID detects the inductor current _IL ; the comparator AC1 will preset the valley current I _v is compared with the inductor current _IL ; when the inductor current _IL is lower than the preset valley current I _v , the output signal V _C1 of the comparator AC1 is at a high level, otherwise, when _IL is lower than I _v , V _C1 is at low level; when the inductor current I _L is lower than the preset valley current I _v , the switch tube S of the converter is turned on, and I _L starts to rise, and the output signal V _C1 of the comparator AC1 is a series of narrow pulse signals.

The pulse selector PS completes the comparison of the output voltage and the selection of the control pulse: Figures 2 and 4 show that the comparator AC2 compares the output voltage V _o with the reference voltage V _ref , when the output voltage V _o is lower than the reference voltage V _ref , _the output signal V _C2 of comparator AC2 is low level, on the contrary, when V _o is lower than V _ref , V _C2 is high level; The output signal V _{C2 of} V C2 is output to the Q terminal to generate the pulse selection signal V _Q . According to the working principle of the flip-flop: V _Q remains unchanged before the next rising edge of V _C1 comes, and The level of the level is always opposite to V _Q.

The pulse generator PG completes the generation and output of the control pulse: Figures 2 and 5 show that when the rising edge of V _C1 comes, the S terminal of the RS flip-flop RSFF1 inputs a high level, and the control pulse signal _PL output by RSFF1 is a high level Level, when the one-shot timer OOT1 ends, the R terminal of the RS flip-flop RSFF1 inputs a high level, and the control pulse signal _PL output by RSFF1 becomes a low level; the working process of the RS flip-flop RSFF2 is similar to the above-mentioned RSFF1 , but because the R terminal of RSFF2 is connected to the one-shot timer OOT2, the time length of the one-shot timer OOT2 is longer than the time length of the one-shot timer OOT1, and the high level duration of the control pulse signal P _H output by RSFF2 is longer than P _L ; when the pulse selection signal V _Q is high level, When it is low level, the AND gate AG1 is opened, AG2 is blocked, and the OR gate OG outputs the control pulse _PL to the drive circuit; otherwise, when the pulse selection signal V _Q is low level, When it is high level, the AND gate AG2 is opened, AG1 is blocked, and the OR gate OG outputs the control pulse P _H to the driving circuit.

The converter in this example is a Buck converter.

Use PSIM software to carry on time domain simulation analysis to the method of this example, the result is as follows.

FIG. 6 is a simulated working waveform of a converter using the above-mentioned control method and its control device in a rated working state. Fig. 6a, Fig. 6b, Fig. 6c, Fig. 6d, Fig. 6e, Fig. 6f respectively show the converter inductor current I _L , the clock pulse signal V _C1 at the beginning of the switching period, the control pulse signal _PH , the control pulse signal _PL , the effect Control pulse signal V _P and converter output voltage V _o . It can be seen from Fig. 6 that 13 switching cycles constitute a cycle, and the pulse sequence composed of the control pulses of the switching tube S is: 1P _H —5P _L —1P _H —6P _L . There is no low-frequency fluctuation phenomenon in the converter, and the output voltage ripple of the converter is about 17mV.

Fig. 7 is the working waveform of the existing pulse sequence control converter under the rated working condition. Figure 7a, Figure 7b, and Figure 7c are time-domain simulation waveform diagrams of the P _H pulse in the effective control pulse signal of the converter, the P _L pulse in the effective control pulse signal, and the output voltage V _o of the converter, respectively. It can be seen from Fig. 6 that when the converter works in the continuous mode, the control pulse signal _PH and the control pulse signal _PL are continuously used as effective control pulses, the converter output has low-frequency fluctuations, and the converter output voltage ripple is about 0.85V , much larger than the converter output voltage ripple 17mV in Embodiment 1 of the present invention. Therefore, adopting the converter of the present invention can suppress the low-frequency fluctuation phenomenon of the pulse sequence control continuous operation mode switching converter, so that the working range of the controlled converter is not limited by the critical condition of the inductance current of the pulse sequence control converter.

Embodiment two

Fig. 8 shows that this example is basically the same as the first example, except that the converter TD of the switching power supply controlled by this example is a Boost converter.

Embodiment Three

FIG. 9 shows that this example is basically the same as the first example, except that the converter TD of the switching power supply controlled by this example is a Buck-Boost converter.

The method of the present invention can be realized with analog device or digital device conveniently; Except the switching power supply that can be used for the converter in the above embodiment to form, also can be used for Cuk converter, BIFRED converter, flyback converter, half-bridge converter , full-bridge converter and other power circuits to form a switching power supply.

Claims (5)

1. half of continuous operation mode Switching Power Supply stagnant ring pulse sequence control method, half stagnant ring pulse train regulating system of continuous operation mode Switching Power Supply is made up of converter TD and controller, its working method comprises: at each switch periods initial time, according to the effective control impuls in this switch periods of switch converters output voltage control pulse choice rules selection, thus realize the control to continuous operation mode switch converters; Its control impuls selective rule is: if V _olower than V _ref, adopt control impuls P _hswitching tube S in gauge tap converter; Otherwise, if V _ohigher than V _ref, adopt control impuls P _lgauge tap pipe S;

Produce control impuls P _hmethod be:

At the t that certain switch periods is initial ₀in the moment, single triggered timer starts timing, control impuls P _hbecome high level from low level, the switching tube S in converter TD is open-minded, inductive current I _lrise; At t ₀+ τ _{on_H}in the moment, single triggered timer terminates timing, control impuls P _hat maintenance high level set time τ _{on_H}after become low level, switching tube S turns off, and diode D is open-minded, inductive current decline; Default inductive current valley I is dropped at inductive current _vmoment, control impuls P _hat maintenance low level time τ _{off_H}after become high level, single triggered timer starts timing again, and switching tube S is again open-minded, and converter enters next switch periods;

Produce control impuls P _lmethod and above-mentioned generation control impuls P _hmethod similar, difference be control impuls P in a switch periods _lfor the low level duration is τ _{on_L}, τ _{on_L}< τ _{on_H};

Described default inductive current valley I _vproduce for the inductive current valley that directly sets or by input, output feedack amount, the inductive current valley relevant with input quantity or output quantity;

The duration τ of described default high level _{on_H}with low level duration τ _{on_L}for the constant on-time directly set, or produced by input, output feedack amount, the constant on-time relevant with input quantity or output quantity.

2. one kind realizes the device of half stagnant ring pulse sequence control method of continuous operation mode Switching Power Supply described in claim 1, be made up of converter TD and controller, controller comprises voltage detecting circuit VD, current detecting and comparison circuit IDC, pulse selector PS, pulse generator PG, single triggered timer OOT1, single triggered timer OOT2, drive circuit DR, it is characterized in that: current detecting is connected with pulse selector PS, pulse generator PG, single triggered timer OTT1, single triggered timer OTT2 with comparison circuit IDC; Voltage detecting circuit VD, pulse selector PS, pulse generator PG, drive circuit are connected to DR successively; Pulse generator PG is connected with comparison circuit IDC, single triggered timer OOT1, single triggered timer OOT2 with current detecting.

3. device according to claim 2, is characterized in that: described current detecting and comparison circuit IDC specifically consist of: the positive polarity termination of comparator AC1 presets valley point current I _v, the inductive current I that negative polarity termination current detection circuit I D exports _l.

4. device according to claim 2, is characterized in that: specifically consisting of of described pulse selector: be made up of comparator AC2 and d type flip flop DFF; The converter output voltage V of the positive polarity termination voltage detecting circuit VD output of comparator AC2 _o, negative polarity termination reference voltage V _ref, the output of AC2 is held with the D of d type flip flop DFF and is connected.

5. device according to claim 2, is characterized in that: specifically consisting of of described pulse generator: by rest-set flip-flop RSFF1 and rest-set flip-flop RSFF2, with door AG1 and with door AG2, and or door OG form; The S end of rest-set flip-flop RSFF1 and RSFF2 all meets the output signal V of current detecting and comparison circuit _c1, the output signal V of R end difference order triggered timer OOT1 and OOT2 _tLand V _tH; To hold with the Q of the input termination rest-set flip-flop RSFF1 of door AG1 and the Q of trigger DFF holds, hold with the Q of the input termination rest-set flip-flop RSFF2 of door AG2 and trigger DFF end; Or the input termination of door OG and the output of door AG1 and AG2, the drive circuit DR of the output termination switching tube S of OG1.