TWI434483B - Power converting circuit and converting controller - Google Patents

Description

Power conversion circuit and conversion controller

The invention relates to a power conversion circuit and a conversion controller, in particular to a power conversion circuit and a conversion controller with a protection start function.

Today's power conversion circuits are mainly divided into linear and switched power supplies. The linear power conversion circuit has a simple circuit, small chopping, and small electromagnetic interference. However, the electronic components are large, so the circuit is bulky and heavy, and the conversion efficiency is low. Although the switching power conversion circuit is more complicated, and the chopping is relatively large, the electromagnetic interference is relatively large, but due to the advantages of high conversion efficiency and low power consumption during no-load, the current market for power conversion circuits is switched power conversion. The circuit is the mainstream.

The main function of the power conversion circuit is to convert an input power into a suitable driving power source to drive the load. Moreover, in order to avoid damage to the components caused by abnormal circuits, and even endanger the safety of the user, the power conversion circuit stops supplying power to the load when detecting a circuit abnormality. However, when the power conversion circuit is just started and the driving power supply is not stable, the circuit abnormality is misjudged. Therefore, the protection function is generally suspended for a predetermined period of time after startup to avoid misjudgment.

At present, the common protections include over-voltage protection, over-voltage protection, over-current protection, etc. In order to avoid misjudgment of circuit protection that may be encountered when the preset time period is too short, the protection function will be uniformly activated based on the latest protection start point. . However, the unified boot protection mode will prevent other protection functions from being started in time, causing loopholes in protection, making the power conversion circuit unable to fully protect the circuit.

In view of the protection loophole caused by the unified boot protection in the prior art, the present invention starts the protection function at a predetermined timing to achieve timely protection of various protection functions and reduces protection loopholes.

To achieve the above object, the present invention provides a conversion controller for controlling a conversion circuit to perform power conversion on an input power source. The controller includes a duty cycle control unit, a protection start control unit, and a protection unit. The duty cycle control unit controls the power conversion circuit to perform power conversion according to a feedback signal. The protection start control unit outputs a plurality of protection start signals according to the timing result of a timing circuit. The protection unit is configured to detect the conversion circuit and generate a protection signal when determining that the conversion circuit is abnormal, and the duty cycle control unit stops operating according to the protection signal, wherein the protection unit has a plurality of protection functions, and the corresponding protection start signal is activated according to the plurality of protection start signals. Protective function.

The invention also provides a power conversion circuit comprising a conversion circuit and a conversion controller. The conversion circuit is coupled to an input power source to convert power to the input power source to drive a load. The conversion controller returns a signal according to one of the states representing the load, controls the conversion circuit to perform circuit conversion, and starts a corresponding protection function in the plurality of protection functions to stop the power conversion of the conversion circuit when determining that the state of the conversion circuit and the load is abnormal. . The conversion controller starts a plurality of protection functions according to a startup signal by a predetermined protection startup program.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

Referring to the first figure, there is shown a circuit diagram of a protection start control unit applied to a conversion controller according to a first preferred embodiment of the present invention. The protection start control unit 100 includes a timing circuit having a capacitor C, a charging circuit and a timing comparison circuit 110. The charging circuit includes a first charging current source I1, a second charging current source I2, and a charging current. Adjust the switch SW. Timing comparison circuit 110 includes comparators 112, 114, 116. The non-inverting input terminals of the three comparators 112, 114, and 116 are coupled to the capacitor C, and the inverting terminals respectively receive the reference signals V1, V2, and V3, wherein the reference signal V1 is lower than the reference signal V2. The reference signal V2 is lower than the reference signal V3. In addition, the protection start control unit 100 includes a reset unit that receives an undervoltage lockout protection signal UVLO, an enable signal EN, and a protection signal PROT to determine the timing start point of the protection start control unit. The reset unit includes a reverse gate 124 and a reset switch SWre. When resetting, the capacitor C is discharged, and the voltage Vc on the capacitor C is reset to zero, so that the timing circuit is re-timed. In this embodiment, the conversion controller has not been activated (the startup signal EN is at a low level), the driving voltage received by the conversion controller is not sufficiently high (the undervoltage lockout protection signal UVLO is at a low level), and the circuit is abnormal ( The protection signal PROT is at a low level. When either of these conditions occurs, the anti-gate 124 will turn on the reset switch SWre to redesign the circuit. Therefore, the timing at which the protection start control unit 100 of the present embodiment starts timing is determined according to the start signal EN and the like, and is restarted when the driving voltage is insufficient or any circuit abnormality occurs.

Please also refer to the second figure, which is a corresponding timing diagram of the embodiment shown in the first figure. When the reset switch SWre is turned off at the time point t0, the voltage Vc of the capacitor C starts to rise, so that the comparators 112, 114, and 116 sequentially output the high-level protection start signal Pe1 at the time points t1, t2, and t3, respectively. Pe2 and Pe3 respectively activate the protection function circuits P1, P2 and P3 in a protection unit 120, and the protection function circuit can be an Over Voltage Protection circuit, an Over Voltage Protection circuit, and an excessively high voltage. Over Current Protection circuit, or Under Current Protection circuit, Over Temperature Protection circuit, etc. At time t4, any protection function circuit P1, P2, P3 in the protection unit 120 detects that the circuit state corresponding to the detection is abnormal after starting, and outputs a low level protection signal PROT through the inverse OR gate 122. , the conversion controller enters the protection state. At the same time, the reset unit discharges the capacitor C to zero the voltage Vc.

The protection start control unit 100 can simultaneously control an input switch SWf to determine whether to stop the power input to the power source Vin to continue input to the conversion controller. The controlled conversion circuit 130 prevents components in the circuit from being damaged when a circuit abnormality occurs. The input switch SWf is coupled between the input power source Vin and the conversion circuit 130. A protection switch SWp and a protection resistor Rf are connected in series between the input power source Vin and the ground, and the connection point is connected to the control terminal of the input switch SWf. When the voltage Vc of the capacitor C in the protection start control unit 100 is reset to zero, the protection switch SWp is turned off, and at this time, the potential of the connection point of the protection switch SWp and the protection resistor Rf will rise to the same potential as the input power source Vin, so that the input switch The SWf is also turned off and the power of the input power source Vin is stopped to be input to the conversion circuit 130.

The starting sequence of the above protection function circuit can be determined according to the actual circuit. Generally, the closer the circuit protection starting point is to the input power source, the current protection is prioritized over the voltage protection, and the weaker component protection is prioritized over the specification. Strong component protection. Therefore, different circuit designs have different protection startup procedures. The protection start control unit of the present invention can be predetermined to protect the startup program according to the actual circuit design, and sequentially activates these protection functions.

The timing circuit can determine the protection start time of the protection function circuits P1, P2, and P3 in the protection unit 120 early or late through the reference signals V1, V2, and V3 and the charging current setting of the charging circuit. In addition, since the comparator has a range limit of the detectable level, the level of too low or too high may not be detected due to noise, etc., so the time timing may have difficulty limiting. Therefore, the charging circuit of the present invention can adjust the magnitude of the charging current according to the protection start signal of the timing comparison circuit 110 to obtain a shorter or longer timekeeping function. In the present embodiment, in the time t0-t1, the charging circuit simultaneously charges the capacitor C with the currents of the first charging current source I1 and the second charging current source I2, and the voltage Vc of the capacitor C quickly reaches the level of the reference signal V1. When the comparator 112 outputs the high-level protection enable signal Pe1, the charging current adjustment switch SW will be turned off, and at this time, the charging circuit charges the capacitor C only by the current of the first charging current source I1. In addition, the timing circuit can determine the starting point of each protection function by using the charging potential of the capacitor, and can also use a conventional timing method such as a method in which the clock generator generates a pulse signal and counts the number of pulse signals. The practice of capacitor charging and conventional soft The use of capacitor charging to gradually increase the duty cycle during startup is similar, so the above two circuits can be used in combination with each other. Please refer to the description of the following examples for this part.

Referring to the third figure, there is shown a circuit diagram of a power conversion circuit according to a first embodiment of the present invention. The power conversion circuit includes a conversion circuit 230 and a conversion controller 250. The conversion circuit 230 is coupled to an input power source Vin to convert the power of the input power source Vin to drive a load 235. The conversion controller 250 returns the signal VFB according to one of the states representing the load to control the conversion circuit 230 to perform circuit conversion. In this embodiment, the conversion circuit 230 is a DC-DC converter circuit including a first switch SW1, a second switch SW2, an inductor L, and an output capacitor Co. The switching controller 250 controls the on and off of the first switch SW1 and the second switch SW2 according to the feedback signal VFB generated by the voltage detecting circuit VD to reduce the voltage of the input power source Vin to a stable output voltage Vout. To drive the load 235.

The conversion controller 250 includes a protection start control unit 200, a soft start circuit 205, a protection unit 220, and a duty cycle control unit 240. The soft start circuit 205 generates a soft start signal SS after receiving the start signal EN, and the duty cycle control unit 240 receives the soft start signal SS and performs a soft start procedure accordingly, so that the conduction period specific gravity (duty cycle) of the first switch SW1 is gradually increased. Increased to avoid excessive Ripple caused by an excessively fast start-up cycle. The protection start control unit 200 determines the timing start point according to the start signal EN, and outputs a plurality of protection start signals Pe to the protection unit 220 according to the predetermined startup program to sequentially activate the protection function corresponding to the protection unit 220. In this embodiment, the soft start signal SS is a signal that rises with time, and can replace the function of the voltage Vc as shown in the first figure as a timing basis for protecting the startup control unit 200. The protection unit 220 detects the circuit and generates a protection signal PROT when the state of the conversion circuit and the load is abnormal, so that the duty cycle control unit 240 stops operating. In this embodiment, the protection unit 220 determines whether the output voltage Vout is too high or too low, and whether the load current Iload is too high or too high, based on the feedback signal VFB, the load current signal Ise, and the current detection signal Cse. Low and whether the input current is too high or too low, and when any of the above circuit abnormal conditions occurs, or occurs and a predetermined time elapses, a protection signal PORT is generated to the duty cycle control unit 240 to cause the conversion controller 250 to enter the protection mode. The conversion circuit 230 is stopped to perform circuit conversion. The protection signal PORT is simultaneously output to the protection start control unit 200 to reset the timing of the protection start control unit 200.

Please refer to the fourth figure, which is a circuit diagram of a power conversion circuit according to a second embodiment of the present invention. The power conversion circuit includes a conversion circuit 330 and a conversion controller 350 for converting the power of an input power source Vin to drive a load 335. In this embodiment, the load 335 is a light-emitting diode module.

The conversion controller 350 controls the conversion circuit to perform power conversion according to the current detection signal Cse (in the present embodiment, the current detection signal Cse is used as the feedback signal). In this embodiment, the conversion circuit includes a switch M, an inductor L, and a diode D. A current detecting resistor Rse is coupled to the switch M to generate a current detecting signal Cse according to the current of the load. The voltage detecting circuit VD is coupled to the negative end of the load 335 to generate a voltage detecting signal Vse according to the voltage across the load 335. An input switch SWf is coupled between the input power source Vin and the conversion circuit 330. A protection switch SWp and a protection resistor Rf are connected in series between the input power source Vin and the ground, and the connection point is connected to the control terminal of the input switch SWf. When the conversion controller 350 determines that the circuit is abnormal, the input switch SWf is turned off through the protection switch SWp and a protection resistor Rf. At this time, the power of the input power source Vin will be stopped and input to the conversion circuit 330 to reach the protection conversion circuit 330 and the load. 335 features. In addition, a driving voltage circuit includes an input resistor Rin, an input capacitor Cin and a Zener diode Ze coupled to the input power source Vin to provide a driving voltage VDD to the conversion controller 350.

The conversion controller 350 includes a protection start control unit 300, a protection unit 320, and a duty cycle control unit 340. The duty cycle control unit 340 determines the current of the load 335 according to the current detection signal Cse, and turns off the switch M when the current of the load 335 reaches the upper limit value, and turns on the switch M again after a fixed off time to make the current of the load 335 Maintained within a predetermined range. The duty cycle control unit 340 further performs pulse dimming on the load 335 according to a dimming signal DIM.

The protection start control unit 300 determines the timing start point according to the start signal EN and the dimming signal DIM, and outputs a plurality of protection start signals Pe to the protection unit 320 according to the predetermined startup program to activate the protection function corresponding to the protection unit 320. The protection start control unit 300 of the embodiment can restart the timing when the dimming signal DIM is represented as “ON”, and the protection of the dimming signal DIM is “OFF” to prevent the dimming signal DIM from being represented. When it is "OFF", it may be misjudged as a circuit abnormality.

The protection unit 320 detects the circuit and generates a protection signal PROT when the state of the conversion circuit and the load is abnormal, so that the duty cycle control unit 340 stops operating. In this embodiment, the protection unit 320 determines, according to the voltage detection signal Vse and the current detection signal Cse, whether the number of short-circuits of the light-emitting diodes in the negative electrode 335 is excessive, and whether the load current is too high, and When any of the above circuit abnormalities occurs and a predetermined time elapses, the protection signal PORT is generated to the duty cycle control unit 340, causing the conversion controller 350 to enter the protection mode to stop the conversion circuit 330 for circuit conversion. The protection signal PORT is simultaneously output to the protection start control unit 300 to reset the timing of the protection start control unit 300.

The above embodiment activates the corresponding protection function at a predetermined timing, and the activation can initiate these protection functions in a one-to-one or one-to-many manner (i.e., multiple protections are initiated at the same time point). In addition, the present invention can still determine which protection functions can be activated early according to the state of the circuit to achieve better protection.

Referring to FIG. 5, a circuit diagram of a protection start control unit applied to a conversion controller according to a second preferred embodiment of the present invention. The protection start control unit 400 includes a capacitor C, a charging circuit and a timing comparison circuit 410. The charging circuit includes a first charging current source I1, a second charging current source I2, and a charging current adjustment switch SW. Timing comparison circuit 410 includes comparators 411, 412, 413, 414 and or gates 417, 418. The non-inverting input terminals of the comparators 412 and 414 are coupled to the capacitor C, and the inverting terminal receives the reference signals V1 and V2, wherein the reference signal V1 is lower than the reference signal V2. The non-inverting input of the comparator 411 receives the current detecting signal Cse, and the inverting terminal receives the reference signal V1', respectively. The non-inverting input of the comparator 413 receives the voltage detecting signal Vse, and the inverting terminal receives the reference signal V2'. The OR gate 417 receives the output signals of the comparators 411 and 412 to output a protection enable signal Pe1 to the protection function circuit P1 of the protection unit 420. The OR gate 418 receives the output signals of the comparators 413, 414 to output a protection enable signal Pe2 to the protection function circuit P2 of the protection unit 420. In addition, the protection start control unit 400 includes a reset unit that receives an undervoltage lockout protection signal UVLO, an enable signal EN, a dimming signal DIM, and a protection signal PROT to determine a timing start point for protecting the startup control unit. The reset unit includes a reverse gate 424 and a reset switch SWre. When resetting, the capacitor C is discharged, and the voltage Vc on the capacitor C is reset to zero, so that the timing circuit is re-timed. The protection start control unit 400 can control an input switch SWf through a protection switch SWp and a protection resistor Rf connected in series between the input power source Vin and the ground, and stop the input power switch Vin when the circuit is abnormal, and stop the power input to the power supply Vin to continue to input the conversion circuit. 430.

The protection function circuit P1 receives the current detection signal Cse to determine whether the current detected by the current detection signal Cse is abnormal. When the current has risen to a predetermined value (represented by reference signal V1'), the representative can start to judge the current. Therefore, even if the comparator 412 has not output the high level signal, or the gate 417 can generate the protection enable signal Pe1 according to the high level signal output from the comparator 411, the protection function circuit P1 is activated. Similarly, the protection function circuit P2 receives the voltage detection signal Vse to determine whether the voltage detected by the voltage detection signal Vse is abnormal. When the voltage has risen to a predetermined value (represented by reference signal V2'), the representative can begin to judge the voltage. Therefore, even if the comparator 414 has not output the high level signal, or the gate 418 can still generate the protection enable signal Pe2 according to the high level signal outputted by the comparator 413, the protection function circuit P2 is activated.

As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims.

100, 200, 300, 400. . . Protection start control unit

110, 410. . . Timing comparison circuit

112, 114, 116, 411, 412, 413, 414. . . Comparators

120, 220, 320, 420. . . Protection unit

122,422. . . Reverse or gate

124,424. . . Reverse gate

130, 230, 330, 430. . . Conversion circuit

205. . . Soft start circuit

235, 335. . . load

240, 340. . . Work cycle control unit

250, 350. . . Conversion controller

417, 418. . . Gate

C. . . capacitance

I1. . . First charging current source

I2. . . Second charging current source

SW. . . Charging current adjustment switch

V1, V1', V2, V2', V3. . . Reference signal

UVLO. . . Undervoltage lockout protection signal

EN. . . Start signal

PROT. . . Protection signal

SWre. . . Reset switch

Vc. . . Voltage

T1, t2, t3, t4. . . Time point

Pe, Pe1, Pe2, Pe3. . . Protection start signal

P1, P2, P3. . . Protection function circuit

SWf. . . Input switch

Vin. . . Input power

SWp. . . Protection switch

Rf. . . Protection resistor

VFB. . . Signal number

230. . . Conversion circuit

SW1. . . First switch

SW2. . . Second switch

L. . . inductance

Co. . . Output capacitor

VD. . . Voltage detection circuit

Vout. . . The output voltage

SS. . . Soft start signal

Ise. . . Load current signal

Cse. . . Current detection signal

Iload. . . Load current

M. . . switch

D. . . Dipole

Vse. . . Voltage detection signal

Rin. . . Input resistance

Cin. . . Input capacitance

Ze. . . Zener diode

The first figure is a circuit diagram of a protection start control unit applied to a conversion controller in accordance with a first preferred embodiment of the present invention.

The second figure is a corresponding timing diagram of the embodiment shown in the first figure.

The third figure is a circuit diagram of a power conversion circuit according to a first embodiment of the present invention.

The fourth figure is a circuit diagram of a power conversion circuit according to a second embodiment of the present invention.

Figure 5 is a circuit diagram of a protection start control unit applied to a conversion controller in accordance with a second preferred embodiment of the present invention.

100. . . Protection start control unit

110. . . Timing comparison circuit

112, 114, 116. . . Comparators

120. . . Protection unit

122. . . Reverse or gate

124. . . Reverse gate

130. . . Conversion circuit

C. . . capacitance

I1. . . First charging current source

I2. . . Second charging current source

SW. . . Charging current adjustment switch

V1, V2, V3,. . . Reference signal

UVLO. . . Undervoltage lockout protection signal

EN. . . Start signal

PROT. . . Protection signal

SWre. . . Reset switch

Vc. . . Voltage

Pe1, Pe2, Pe3. . . Protection start signal

P1, P2, P3. . . Protection function circuit

SWf. . . Input switch

Vin. . . Input power

SWp. . . Protection switch

Rf. . . Protection resistor

Claims (12)

A conversion controller for controlling a conversion circuit for power conversion of an input power source, the controller comprising: a duty cycle control unit, controlling the conversion circuit for power conversion according to a feedback signal; and a protection start control unit, And outputting a plurality of protection start signals according to a timing result of a timing circuit; and a protection unit for detecting the conversion circuit and generating a protection signal when determining that the conversion circuit is abnormal, and the duty cycle control unit stops operating according to the protection signal The protection unit has a plurality of protection functions, and the corresponding protection function is activated according to the plurality of protection activation signals. The conversion controller of claim 1, wherein the timing circuit starts timing according to an activation signal, a dimming signal, the protection signal, or a combination thereof. The switching controller of claim 2, wherein the timing circuit comprises a capacitor, a charging circuit and a timing comparison circuit, wherein the charging circuit charges the capacitor with a charging current when the timing circuit starts timing. The timing comparison circuit generates the plurality of protection enable signals according to the voltage of the capacitor. The conversion controller of claim 3, wherein the charging circuit adjusts the magnitude of the charging current according to at least one of the plurality of protection activation signals. The conversion controller of claim 1, wherein the timing circuit is a soft start circuit that generates a soft start signal, and the duty cycle control unit performs a soft start process according to the soft start signal. The conversion controller of claim 1, wherein the protection activation control unit further determines whether to output the corresponding protection activation signal of the plurality of protection activation signals according to the at least one detection signal. A power conversion circuit includes: a conversion circuit coupled to an input power source for converting power of the input power source to drive a load; and a conversion controller for controlling the signal according to one of the states representing the load to control The conversion circuit performs circuit conversion, and when determining that the state of the conversion circuit and the load is abnormal, starting a corresponding protection function of the plurality of protection functions to stop power conversion of the conversion circuit; wherein the conversion controller is configured according to an activation signal A predetermined protection launcher initiates a plurality of protection functions. The power conversion circuit of claim 7, further comprising an input control switch coupled to the input power source and the conversion circuit, wherein the conversion controller controls when the state of the conversion circuit and the load is abnormal The input control switch is turned off to decouple the input power source and the conversion circuit. The power conversion circuit of claim 7 or 8, further comprising a driving voltage circuit coupled to the input power source to generate a driving voltage to the conversion controller to provide operation of the conversion controller electric power. The power conversion circuit of claim 7, wherein the load comprises at least one light emitting diode, and the conversion controller performs a pulse dimming process on the light emitting diode according to a dimming signal, the conversion The controller further activates a plurality of protection functions according to the dimming signal by the predetermined startup program. The power conversion circuit of claim 7, wherein the conversion controller includes a timing circuit for timing, and the conversion controller activates the plurality of protection functions according to a timing result of the timing circuit. The power conversion circuit of claim 11, wherein the conversion controller further determines whether to activate the corresponding protection function of the plurality of protection functions according to the at least one detection signal.