Synchronous rectification device and method thereof

A synchronous rectification device is adapted to control a conversion circuit, where he conversion circuit includes: a primary side coil, configured to receive input power; and a secondary side coil, configured to generate inductive power in response to the input power. The synchronous rectification device includes: a first control circuit, configured to provide a first control signal to control the primary side coil; a secondary side switch, configured to generate an ON signal and an OFF signal according to the inductive power; an isolation coupling element; and a second control circuit. The isolation coupling element includes: a receiving side, configured to receive the first control signal; and a reaction side, configured to generate a coupling signal in response to the first control signal. The second control circuit outputs a second control signal according to the coupling signal, the ON signal, and the OFF signal to adjust the inductive power.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. § 119(a) to Patent Application No. 107142566 filed in Taiwan, R.O.C. on Nov. 28, 2018, the entire contents of which are hereby incorporated by reference.

BACKGROUND

Technical Field

The present disclosure relates to the field of power conversion, and in particular, to a synchronous rectification device and a method thereof.

Related Art

With the progress and development of technologies, electronic products become increasingly diverse, and different electronic products need to operate at different voltages or different currents. As a result, many different power supplies have been developed to meet needs, and to facilitate the increasingly flourishing of the power conversion technology. Therefore, the power conversion technology belongs to a relatively important part in the electronics industry.

Currently, in the power supplies, to achieve a high efficiency and low loss rectification function, a synchronous rectification device has become an important and indispensable core part. The same as other types of rectification devices do, the synchronous rectification device includes a primary side switch and a secondary side switch. However, in the conventional synchronous rectification device, due to a parasitic element or a signal surge in a circuit, the primary side switch and the secondary side switch may be turned on simultaneously, which causes a short circuit in the synchronous rectification device. When a short circuit occurs in the synchronous rectification device, additional power loss and unnecessary electromagnetic interference may occur, and elements in the synchronous rectification device may be damaged. Consequently, the synchronous rectification device cannot operate properly.

SUMMARY

In view of this, the present disclosure provides a synchronous rectification device, adapted to control a conversion circuit. The conversion circuit includes a primary side coil and a secondary side coil, the primary side coil is configured to receive input power, and the secondary side coil is configured to generate inductive power in response to the input power. The synchronous rectification device includes a first control circuit, a secondary side switch, an isolation coupling element, and a second control circuit. The first control circuit is configured to provide a first control signal. The secondary side switch is configured to generate an ON signal and an OFF signal according to the inductive power. The isolation coupling element includes a receiving side and a reaction side. The receiving side is configured to receive the first control signal. The reaction side is configured to generate a coupling signal in response to the first control signal. The second control circuit is configured to output a second control signal according to the coupling signal, the ON signal, and the OFF signal to adjust the inductive power.

According to some embodiments, the secondary side switch is configured to be turned on or off according to the second control signal to adjust the inductive power.

According to some embodiments, the synchronous rectification device further includes a primary side switch. The primary side switch is configured to be turned on or off according to the first control signal. When the primary side switch is on, the secondary side switch is off According to some embodiments, the second control circuit adjusts the second control signal according to the OFF signal to turn off the secondary side switch.

According to some embodiments, the second control circuit includes a level generating circuit. The level generating circuit is configured to provide a judgment level for the second control circuit to adjust the second control signal.

According to some embodiments, the level generating circuit adjusts the judgment level to a first level in response to the coupling signal.

According to some embodiments, the level generating circuit adjusts the judgment level to a second level in response to the ON signal.

According to some embodiments, when the judgment level is the first level, the second control circuit adjusts the second control signal according to the ON signal to turn on the secondary side switch.

According to some embodiments, the synchronous rectification device further includes a counting circuit. The counting circuit is configured to adjust the judgment level according to a counting time.

According to some embodiments, when a duration during which the judgment level is the first level exceeds the counting time, the counting circuit adjusts the judgment level to the second level.

According to some embodiments, a synchronous rectification device method includes: converting input power into inductive power according to a first control signal; generating an ON signal and an OFF signal according to the inductive power; generating a coupling signal in response to the first control signal; outputting a second control signal according to the coupling signal, the ON signal, and the OFF signal; and adjusting the inductive power according to the second control signal.

According to some embodiments, the synchronous rectification device method further includes adjusting the second control signal according to a judgment level, where the judgment level is adjusted to a first level in response to the coupling signal, and the judgment level is adjusted to a second level in response to the ON signal.

According to some embodiments, the synchronous rectification device method further includes adjusting the judgment level according to a counting time, where when a duration during which the judgment level is the first level exceeds the counting time, the judgment level is adjusted to the second level.

In conclusion, according to the synchronous rectification device and the method thereof of the present disclosure, the second control signal is output according to the coupling signal, the ON signal, and the OFF signal to adjust the inductive power. The synchronous rectification device can prevent a short circuit case caused when the primary side switch and the secondary side switch are turned on simultaneously. In some embodiments, the synchronous rectification device and the method thereof further include adjusting the judgment level according to the counting time. Therefore, the synchronous rectification device has a reset function.

DETAILED DESCRIPTION

In the present disclosure, the word “coupling” and derivatives thereof may be used. In some embodiments, “coupling” may be used to represent that two or more elements are either in direct physical or electrical contact, or may mean that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other.

FIG. 1is a block diagram of a synchronous rectification device100according to some embodiments of the present disclosure. In some embodiments, a power supplier10includes a conversion circuit20and a synchronous rectification device100. The conversion circuit20is configured to receive input power Sinand generate inductive power Soutin response to the input power Sin, and the synchronous rectification device100is adapted to control the conversion circuit20.

Still refer toFIG. 1, the synchronous rectification device100includes a secondary side switch120, a first control circuit200, a second control circuit300, and an isolation coupling element400. The first control circuit200and the second control circuit300are separately coupled to the conversion circuit20, and the isolation coupling element400is coupled between the first control circuit200and the second control circuit300. The first control circuit200and the second control circuit300are configured to control the conversion circuit20, so that the conversion circuit20can convert the input power Sininto the inductive power Sout. The first control circuit200provides a first control signal SSWto control the conversion circuit20, and the conversion circuit20receives the input power Sinaccording to the first control signal SSW. The second control circuit300outputs a second control signal SSRto control the conversion circuit20, and the conversion circuit20generates the inductive power Soutaccording to the second control signal SSR. In addition, the secondary side switch120generates an ON signal SONand an OFF signal SOFFin response to the inductive power Sout. The isolation coupling element400is configured to generate a coupling signal SCOin response to the first control signal SSW. Specifically, the second control signal SSRoutput by the second control circuit300adjusts the inductive power Soutby using the secondary side switch120. The second control circuit300outputs the second control signal SSRaccording to the coupling signal SCO, the ON signal SON, and the OFF signal SOFF.

Based on the above, operations between the first control circuit200and the second control circuit300should be specifically noted. The first control circuit200controls the second control circuit300by using the isolation coupling element400and the conversion circuit20.

In some embodiments, the power supplier10operates in, for example but not limited to, a situation in which an alternating current (AC) is converted to a direct current (DC). The power supplier10further includes a rectification circuit (not shown). The rectification circuit is configured to convert an externally input AC power (not shown) into a DC input power Sinfor the conversion circuit20to receive. The input power Sinand the inductive power Soutprocessed by the conversion circuit20are DC power.

Still refer toFIG. 1, in some embodiments, the conversion circuit20includes a primary side coil L1and a secondary side coil L2. The primary side coil L1is configured to receive input power Sin, and the secondary side coil L2is configured to generate inductive power Soutin response to the input power Sin. Energy conversion between the primary side coil L1and the secondary side coil L2is implemented by electromagnetic induction. Specifically, when the primary side coil L1receives the input power Sinaccording to the first control signal SSW, the inductive power Soutgenerated by the secondary side coil L2in response to the input power Singradually decreases. On the contrary, when the primary side coil L1does not receive the input power Sinaccording to the first control signal SSW, the inductive power Soutgenerated by the secondary side coil L2in response to the input power Singradually increases.

FIG. 2is a circuit diagram of a synchronous rectification device100according to some embodiments of the present disclosure. In some embodiments, a power supplier10includes two input ends Nin. The two input ends Ninare configured to receive input power Sin, and a primary side coil L1is configured to transfer energy to a secondary side coil L2according to the input power Sin.

Still refer toFIG. 2, in some embodiments, the synchronous rectification device100further includes a primary side switch110. The primary side switch110has a control electrode Eg, a first electrode Ed, and a second electrode Es. The control electrode Egof the primary side switch110is coupled to a first control circuit200. The primary side coil L1is coupled between one end of the two input ends Ninand the first electrode Ed. The other end of the two input ends Ninis coupled to the second electrode Es. The primary side switch110is turned on or off according to a first control signal SSW. Specifically, the control electrode Egturns on or off the first electrode Edand the second electrode Esof the primary side switch110according to a change of the first control signal SSW. Moreover, when the first electrode Edand the second electrode Esof the primary side switch110are on, the primary side coil L1receives the input power Sin. When the first electrode Edand the second electrode Esof the primary side switch110are off, the primary side coil L1does not receive the input power Sin. In other words, the first control signal SSWoutput by the first control circuit200controls the primary side coil L1by using the primary side switch110.

FIG. 3is a signal diagram of a synchronous rectification device100according to some embodiments of the present disclosure. A horizontal axis of the signal diagram is time T, and a vertical axis of the signal diagram is a first control voltage VSW, a coupling voltage VCO, a judgment level VFL, an inducting voltage VSE, and a second control voltage VSR. In some embodiments, the first control circuit200is a pulse width modulation (PWM) controller, and the first control signal SSWis a periodic square wave. The first control signal SSWfor each cycle is composed of a high level and a low level, and a duration of each cycle is fixed. The first control circuit200controls ratios of the high level and the low level respectively in the duration of each cycle. According to some embodiments, when the first control signal SSWis at a high level, the primary side switch100is on.

Still refer toFIG. 2, in some embodiments, the power supplier10includes two output ends Nout. The two output ends Noutare configured to output the inductive power Sout, and the secondary side coil L2is configured to receive the energy transferred by the primary side coil L1to generate the input power Sout.

Still refer toFIG. 2, in some embodiments, the synchronous rectification device100further includes a secondary side diode D2. The secondary side switch120has a control end Ng, a first end Nd, and a second end Ns. The secondary side diode D2is coupled between the first end Ndand the second end Nsof the secondary side switch120. The control end Ng, the first end Nd, and the second end Nsof the secondary side switch120are separately coupled to the second control circuit300. The secondary side coil L2is coupled between one end of the two output ends Noutand the first end Nd. The other end of the two output ends Noutis coupled to the second end Ns. The secondary side switch120is turned on or off according to the second control signal SSR. Specifically, the control end Ngturns on or off the first end Ndand the second end Nsof the secondary side switch120according to a change of the second control signal SSR. The secondary side diode D2is configured to enable the inductive power Soutto flow between the first end Ndand the second end Nswhen the secondary side switch120is turned off. According to some embodiments, the secondary side diode D2is a parasitic element of the secondary side switch120.

In some embodiments, the first control circuit200controls the second control circuit300by using the isolation coupling element400and the conversion circuit20, and therefore, a time for which the second control signal SSRenables the secondary side switch120to be on does not overlap a time for which the first control signal SSWenables the primary side switch110to be on. In other words, when the primary side switch110is on, the secondary side switch120is off. Therefore, the synchronous rectification device100can prevent a short circuit case caused when the primary side switch110and the secondary side switch120are turned on simultaneously.

Referring toFIG. 2andFIG. 4together,FIG. 4is a signal diagram of an inducting voltage VSEaccording to some embodiments of the present disclosure. A horizontal axis of the signal diagram is time T, and a vertical axis of the signal diagram is a first control voltage VSW, an operating voltage VDS, an inducting voltage VSE, and a second control voltage VSR. In some embodiments, the secondary side switch120has the operating voltage VDS. The operating voltage VDSis a potential difference between the first end Ndand the second end Ns, and varies under an impact of the inductive power Sout. Specifically, when the inductive power Soutpasses through the secondary side switch120or the secondary side diode D2, charge accumulated between the first end Ndand the second end Nsof the secondary side switch120increases or decreases along a direction of current of the inductive power Sout, and therefore, a magnitude of the operating voltage VDSvaries with the inductive power Sout. When the operating voltage VDSmeets one of a plurality of inducting voltages VSE(an ON voltage VONand an OFF voltage VOFFare both inducting voltages VSE), the secondary side switch120generates a corresponding ON signal SONor OFF signal SOFF. When the operating voltage VDSmeets the corresponding ON voltage VON, the secondary side switch120generates the corresponding ON signal SON. When the operating voltage VDSmeets the corresponding OFF voltage VOFF, the secondary side switch120generates the corresponding OFF signal SOFF. It should be particularly noted that the signal diagram of the inducting voltage VSEversus time T is merely used to illustrate a time sequence of the ON signal SONand the OFF signal SOFF.

Based on the above, in some embodiments, the secondary side switch is configured to be turned on or off according to the second control signal SSRto adjust the inductive power Sout. When the secondary side switch120is on, since the operating voltage VDScan be regarded as zero, the inductive power Soutis not limited by the secondary side switch120, and the conversion circuit20can normally output the inductive power Sout. When the primary side switch110is turned off, the inductive power Soutis limited by the secondary side diode D2, and therefore, the conversion circuit20cannot normally output the inductive power Sout.

Still refer toFIG. 2andFIG. 3, in some embodiments, the isolation coupling element400includes a receiving side410and a reaction side420. The receiving side410is coupled between the first control circuit200a grounding end GND, and the reaction side420is coupled between the second control circuit300and a reference potential end P1. The receiving side410is configured to receive the first control signal SSW. The reaction side420is configured to generate a coupling signal SCOin response the first control signal SSW. Specifically, the isolation coupling element400is configured to transfer the first control signal SSWoutput by the first control circuit200to the second control circuit300in the form of the coupling signal SCO. When the first control signal SSWflowing through the receiving side410meets a preset threshold of the isolation coupling element400, the reaction side420generates the coupling signal SCOcorresponding to the first control signal SSW, and the reaction side420outputs the coupling signal SCOto the second control circuit300. According to some embodiments, when the first control signal SSWis at a high level, the reaction side420generates the coupling signal SCO, where a duration of the coupling signal SCOcorresponds to a duration during which the first control signal SSWis at a high level.

Based on the above, in some embodiments, the isolation coupling element400is configured to isolate the first control circuit200from the second control circuit300, and to isolate the primary side switch110from the secondary side switch120. Therefore, the isolation coupling element400prevents mutual interference between the primary side switch110and the secondary side switch120due to an abnormal surge. According to some embodiments, the isolation coupling element400is an optical coupler.

Still refer toFIG. 2andFIG. 3, in some embodiments, the second control circuit300outputs the second control signal SSRaccording to the coupling signal SCO, the ON signal SON, and the OFF signal SOFF. The coupling signal SCOand the ON signal SONare configured to drive the second control circuit300to start to output the second control signal SSR. The OFF signal SOFFis configured to drive the second control circuit300to stop outputting the second control signal SSR. In other words, when the second control circuit300receives the OFF signal SOFF, the second control circuit300stops outputting the second control signal SSR, and the secondary side switch120is thus off.

Based on the above, in some embodiments, the second control circuit300further includes a level generating circuit310. The level generating circuit310is configured to provide a judgment level VFLused to adjust the second control signal SSRfor the second control circuit300. The level generating circuit310adjusts the judgment level VFLto a first level F1in response to the coupling signal SCO. The level generating circuit310adjusts the judgment level VFLto a second level F2in response to the ON signal SON.

According to some embodiments, when the judgment level VFLis the first level F1, the second control circuit300adjusts the second control signal SSRaccording to the ON signal SONto turn on the secondary side switch120. In other words, when the second control circuit300needs to receive the ON signal SONand detect that the judgment level VFLis the first level F1, the second control circuit300starts to output the second control signal SSR, and the secondary side switch120is on according to the second control signal SSR. The second control circuit300needs to verify the coupling signal SCOtransferred by the first control circuit200by using the isolation coupling element400and the ON signal SONtransferred by the conversion circuit20. Therefore, the synchronous rectification device100can prevent a short circuit case caused when the primary side switch110and the secondary side switch120are turned on simultaneously.

It should be specifically noted that, in some embodiments, when the level generating circuit310receives the coupling signal SCO, the level generating circuit310switches the judgment level VFLfrom the second level F2to the first level F1. After the level generating circuit310receives the ON signal SONand the second control circuit300starts to output the second control signal SSRto turn on the secondary side switch120, the level generating circuit310switches the judgment level VFLfrom the first level F1to the second level F2.

FIG. 5is a signal diagram of a counting time T1according to some embodiments of the present disclosure. The synchronous rectification device100further includes a counting circuit500coupled to the level generating circuit310. The counting circuit500is configured to adjust the judgment level VFLaccording to a counting time T1. When a duration during which the judgment level VFLis the first level F1exceeds the counting time T1, the counting circuit500adjusts the judgment level VFLto the second level F2. Specifically, when the judgment level VFLis always the first level F1, the secondary side switch120is easily to be incorrectly turned on due to an incorrect ON signal SON. Therefore, the counting circuit500adjusts the judgment level VFLfrom the first level F1to the second level F2to achieve a reset function of the synchronous rectification device100.

FIG. 6is a flowchart of a synchronous rectification method according to some embodiments of the present disclosure. In some embodiments, the synchronous rectification method includes the following steps:

Step S100: Convert input power Sininto inductive power Soutaccording to a first control signal SSW.

Step S120: Generate an ON signal SONand an OFF signal SOFFaccording to the inductive power Sout.

Step S140: Generate a coupling signal SCOin response to the first control signal SSW.

Step S160: Output a second control signal SSRaccording to the coupling signal SCO, the ON signal SON, and the OFF signal SOFF.

Step S180: Adjust the inductive power Soutaccording to the second control signal SSR.

According to some embodiments, the synchronous rectification method further includes: adjusting the second control signal SSRaccording to a judgment level VFL, where the judgment level VFLis adjusted to a first level F1in response to the coupling signal SCOand the judgment level VFLis adjusted to a second level F2in response to the ON signal SON.

According to some embodiments, the synchronous rectification method further includes: adjusting the judgment level VFLaccording to a counting time T1, where when a duration during which the judgment level VFLis the first level F1exceeds the counting time T1, the judgment level VFLis adjusted to the second level F2.

In conclusion, according to the synchronous rectification device100and the method thereof of the present disclosure, the second control signal SSRis output according to the coupling signal SCO, the ON signal SON, and the OFF signal SOFFto adjust the inductive power Sout. The synchronous rectification device100can prevent a short circuit case caused when the primary side switch100and the secondary side switch120are turned on simultaneously. In some embodiments, the synchronous rectification device100and the method thereof further include adjusting the judgment level VFLaccording to the counting time T1. Therefore, the synchronous rectification device100has a reset function.