TWI446695B - Isolation conversion circuits and methods, and lamps using isolated conversion circuits - Google Patents

Description

Isolation conversion circuit and method and luminaire using the same

This invention relates to electronic circuits and, more particularly, to electronic circuits for light emitting elements.

Light Emitting Diode (LED) has attracted much attention in the field of lighting due to its many advantages such as no pollution, long life and vibration resistance, and it has been applied.

The brightness of an LED is usually determined by the average current flowing through it, so it is especially important to accurately control the average current flowing through the LED. In the existing LED electronic circuit, a sampling resistor connected in series with the LED is generally used to sample the current flowing through the LED, and the average current flowing through the LED is accurately controlled by the control of the subsequent controller of the circuit. The isolation conversion circuit 100 shown in FIG. 1 is an LED electronic circuit that typically uses a reversing topology. The isolation conversion circuit 100 obtains an AC input voltage from a wall outlet (grid), converts the AC voltage into a DC voltage through a rectifier bridge, and converts the DC voltage to a desired DC supply voltage through a flyback circuit.

Specifically, the isolation conversion circuit 100 includes a rectifier bridge 101, an input capacitor C _IN , a transformer T, a main switch M, a first sampling resistor R _S , a diode D, an output capacitor C _O , a load sampling resistor R, and a controller 102. The zero crossing detector 103 and the isolation feedback circuit 110. The transformer T is an energy storage component, and includes a primary winding T ₁ , a secondary winding T ₂ and a third winding T ₃ . The rectifier bridge 101 receives the AC input voltage V _IN and converts it into an uncontrolled DC voltage. The input capacitor C _{IN is} connected in parallel to both ends of the rectifier bridge 101, that is, one end of the input capacitor C _IN is coupled to one end of the primary winding T ₁ of the transformer T, and the other end is connected to the ground reference ground. The coupling of the primary winding T _{1 of the} transformer T, the main switch M, the diode D, the secondary winding T _{2 of the} transformer T, and the output capacitor C _O constitutes a typical reversing topology. The manner of coupling is well known to those skilled in the art and will not be described in detail herein. The first sampling resistor R _{S is} coupled in series with the main switch M, and the load sampling resistor R is coupled in series with the LED. The input end of the isolation feedback circuit 110 is coupled to the series coupling point of the load sampling resistor R and the LED, and the output end is coupled to an input end of the controller 102. The input of the zero-crossing detector 103 is coupled to one end of the third winding T ₃ , and the output of the zero-crossing detector 103 is coupled to the other input of the controller 102 . The other end of the third winding T ₃ is coupled to ground. The third input end of the controller 102 is coupled to the series coupling point of the first sampling resistor R _S and the main switch, and the output end of the controller 102 is coupled to the control end of the main switch M.

Since the load sampling resistor R and the LED are coupled in series, the voltage across the load sampling resistor R reflects the current flowing through the LED. The first sampling resistor R _S and the main switch M are coupled in series. Therefore, the voltage across the first sampling resistor R _S reflects the current flowing through the main switch M, that is, the voltage across the first sampling resistor R _S is a current sampling signal. I _sense .

When the isolation conversion circuit 100 is operated, the current flowing through the LED is sent to the controller 102 through the load sampling resistor R and the isolation feedback circuit 110, and the current flowing through the main switch M is sent to the controller 102 through the first sampling resistor R _{S .} . Through the interaction of the zero crossing detector 103, the average current flowing through the LED can be controlled. Since the manner of control is well known to those skilled in the art, for brevity of description, it will not be described in detail herein.

However, this type of control requires an additional load sampling resistor to sample the current flowing through the LED, increasing losses and reducing efficiency. With the development of electronic technology and the improvement of environmental protection requirements, efficiency has become a crucial design factor for power converters. And this control method needs to use the isolation feedback circuit to feed back the load state, which complicates the circuit structure.

Therefore, it is necessary to propose a circuit and method for controlling current sampling of a light-emitting element such as an LED without using a load sampling resistor and an isolation feedback circuit to control the average current.

Therefore, the object of the present invention is to solve the problem that the conventional isolation conversion circuit needs the load sampling resistor to sample the output current, and the isolation feedback circuit needs to feed back the sampled output current, thereby causing the circuit structure to be complicated and the circuit low efficiency.

Based on the above object, the present invention provides a circuit comprising: a transformer comprising a primary winding, a secondary winding and a third winding, the primary winding for receiving an input signal of the isolation conversion circuit, a secondary winding for providing a driving signal to the driven component; a main switch coupled to the primary winding, being turned on and off according to the switching driving signal; and an output current calculator flowing through the main switch during the conduction period a current of the main switch and the switch drive signal, calculating an equivalent value of a current flowing through the driven component; a zero-crossing detector, providing a zero-cross detection signal according to a voltage across the third winding; And providing the switch drive signal according to the equivalent value, a zero-cross detection signal, a current flowing through the main switch during the on-time of the main switch, and a reference signal.

Based on the above object, the present invention also provides a circuit comprising: a transformer comprising a primary winding and a secondary winding, the primary winding for receiving an input signal of the isolation conversion circuit, the secondary winding Providing a driving signal to the driven component; a main switch coupled to the primary winding, being turned on and off according to the switch driving signal; and a zero-crossing detecting capacitor coupled to the primary winding and the main end at one end a series coupling point of the switch, the other end being coupled to the input end of the zero-crossing detector; an output current calculator calculating the flow according to the current flowing through the main switch and the switch driving signal during the main switch being turned on An equivalent value of the current of the driven component; the zero-crossing detector provides a zero-crossing detection signal according to a current flowing through the zero-crossing detection capacitor; the controller, according to the equivalent value, the zero-crossing detection signal, The current flowing through the main switch and a reference signal during the main switch being turned on provide the switch drive signal.

Based on the above object, the present invention also proposes a lamp. The luminaire uses the above described circuit of the present invention.

Based on the above object, the present invention also provides a method for a circuit, the circuit comprising: a transformer comprising a primary winding, a secondary winding and a third winding, the primary winding for receiving the An input signal of the isolation conversion circuit, the secondary winding is configured to provide a driving signal to the driven component; and a main switch coupled to the primary winding and turned on and off according to the switching driving signal, the method comprising the steps : calculating an equivalent value of a current flowing through the driven element according to a current flowing through the main switch during the conduction of the main switch and the switch driving signal; providing zero according to a voltage across the third winding And a cross-detection signal; the switch drive signal is provided according to the equivalent value, a zero-cross detection signal, a current flowing through the main switch during the on-time of the main switch, and a reference signal.

The above-mentioned circuit, method and lamp using the same can sample the output current without load sampling resistor and isolation feedback circuit, thereby simplifying the circuit structure.

As shown in FIG. 2, there is an isolation conversion circuit 200 in accordance with one embodiment of the present invention. This embodiment is used in an AC-DC conversion circuit. However, those skilled in the art will appreciate that the isolation conversion circuit can be used in other circuits, such as DC-DC conversion circuits. The same portion of the isolation conversion circuit 200 and the isolation conversion circuit 100 are given the same reference numerals. The isolation conversion circuit 200 is different from the isolation conversion circuit 100 shown in FIG. 1 in that the isolation conversion circuit 200 does not require a load sampling resistor and The feedback circuit is isolated, and the current sampling and feedback of the LED load is implemented by the output current calculator 104. The equivalent output current I _EQ output by the output current calculator 104 reflects the secondary current.

Specifically, the isolation conversion circuit 200 includes a rectifier bridge 101, an input capacitor C _IN , a transformer T (including a primary winding T ₁ , a secondary winding T _{2 ,} and a third winding T ₃ ), a main switch M, and a first sampling resistor R. _S , diode D, output capacitor C _O , LED. The coupling manner is the same as that of the isolation conversion circuit 100, and the description is concise and will not be described in detail herein. Insulating converter circuit 200 further includes a zero crossing detector 103, an input terminal coupled to the third winding end T _3, T ₃ to detect a third voltage V across winding _T3, and a third voltage V across the winding T ₃ The zero-crossing condition of _T3 provides a zero-crossing detection signal Z _DET to the first input of the controller 102; the output current calculator 104 has a first input coupled to the series coupling of the first sampling resistor R _S and the main switch M a contact to receive the current sampling signal I _sense , the second input end coupled to the output end of the controller 102 to receive the switch drive signal C _TR , and to provide according to the current sampling signal I _sense and the switch drive signal C _TR The output current I _{EQ is} output to the controller 102. The first input end of the controller 102 is coupled to the zero-crossing detector 103 to receive the zero-crossing detection signal Z _DET , and the second input end is coupled to the output current calculator 104 . output terminal to receive the equivalent output current I _EQ, which third input terminal coupled to the first sampling resistor coupled in series point of R _S and M of the main switch to receive the current sense signal I _sense, its fourth input receiving a reference signal R _EF, so that the root Equivalent output current I _EQ, zero-cross detection signal Z _DET, I _sense a current sensing signal and the reference signal R _EF, provides a control terminal of the switch driving signal C _TR calculator 104 and to the output current of the main switch M to control the output current calculating The switch 104 and the main switch M are turned on and off.

In one embodiment, the diode D can be replaced with a rectifier. The main switch M can be any controllable semiconductor switching device such as a metal oxide semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or the like.

In circuit practical applications, the isolation feedback circuit 110 of the prior art isolation conversion circuit 100 typically requires multiple peripheral discrete components to be implemented. However, the isolation conversion circuit 200 of the present embodiment does not need to isolate the feedback circuit. Therefore, the isolation conversion circuit 200 not only reduces the loss but also simplifies the peripheral circuit with respect to the isolation conversion circuit 100. The operation of the isolation conversion circuit 200 will be described below.

When the circuit 200 is running, when the controller 102 provides a high level switch drive signal C _TR to the control terminal of the main switch M, the main switch M is closed and turned on, and the AC input voltage V _IN is passed through the rectifier bridge 101, the input capacitor C _IN , and the original The side winding T ₁ , the main switch M, and the first sampling resistor R _{S are} grounded. The current I _M flowing through the main switch M rises linearly under the action of the magnetizing inductance of the primary winding T ₁ . Accordingly, the voltage across the first sampling resistor R _S also rises linearly. When the current flowing through the main switch M rises to the set peak current I _PK , the switch drive signal C _TR outputted by the controller 102 goes low. Accordingly, the main switch M is turned off. At this time, the polarity of the voltage across the third winding T ₃ is positive and negative, that is, the voltage V _T3 is positive, and the voltage polarity across the secondary winding T ₂ is also positive and negative, and the diode D is turned on and flows through two. The current I _{D of the} polar body D begins to decrease linearly. If the transformer turns ratio of the primary winding T ₁ and the secondary winding T ₂ of the transformer T is n: 1, the peak current of the diode D is n × I _PK . That is, the current I _D flowing through the diode D linearly decreases from n × I _PK . When it falls to zero, the magnetizing inductance of the primary winding T ₁ and the parasitic capacitance (not shown) of the main switch M oscillate. The first zero crossing of the oscillation, that is, when the voltage V _T3 is zero for the first time, the zero crossing detector 103 detects the zero crossing phenomenon and outputs a corresponding zero crossing detection signal Z _DET to the controller 102. The controller 102 receives the zero-cross detection signal Z _DET and outputs a high-level switch drive signal C _TR to turn the main switch M off. The isolation converter circuit 200 enters a new cycle and operates as previously described.

Figure 3 is a flow chart 300 showing the operation of the output current calculator in accordance with the present invention, i.e., a method of calculating the output current of the secondary side of the isolation converter circuit. As shown in FIG. 3, the method includes: Step 301, starting, that is, periodically turning on and off the main switch M of the primary winding of the isolation conversion circuit; Step 302, determining whether the main switch M is in an on state, if the main switch M is conducting. State, proceeding to step 303, sampling the current flowing through the main switch M, the equivalent output current I _{EQ is} set to zero; if the main switch M is in the off state, proceeding to step 304, maintaining the peak current of the main switch M and acting as the main switch M The equivalent output current I _EQ during the on time interval; step 305, provides the equivalent output current I _EQ . That is, the method for calculating the output current of the secondary side of the isolation conversion circuit includes: periodically turning on and off the main switch M of the primary winding of the isolation conversion circuit; sampling the flow through the main switch M during the time interval when the main switch M is turned on The current, the equivalent output current I _{EQ is} set to zero; during the time interval in which the main switch M is turned off, the peak current of the main switch M is maintained and serves as the equivalent output current I _{EQ in the} main switch M off time interval.

4 illustrates an isolation conversion circuit 400 employing the method of calculating the secondary side output current of the isolation conversion circuit of FIG. 3, in accordance with one embodiment of the present invention. The circuit module of the isolation conversion circuit 400 and the same portion of the isolation conversion circuit 200 are given the same reference numerals. For the sake of brevity, the circuit coupling method of the same part will not be described in detail herein. As shown in FIG. 4, the output current calculator 104 includes: a first switch S ₁ , one end coupled to the series coupling point of the first sampling resistor R _S and the main switch M to receive the current sampling signal I _sense ; the first capacitor C _1, a first switch coupled between the other end of the primary side S ₁ and the ground reference; a second switch S _2, a first end coupled to a switch S ₁ is a first capacitor C and _a coupling point; a third The switch S _{3 is} coupled between the other end of the second switch S ₂ and the primary side reference ground. The control ends of the first switch S ₁ , the second switch S ₂ and the third switch S ₃ are coupled to the output of the controller 102, and when the switch drive signal C _TR is at a high level, the first switch S ₁ and the third closing the switch S ₃ is turned on, turned off the second switch S _3; when the switch drive signal C _TR is low, the first switch S ₁ is turned off and the third switch S _3, S ₂ is closed the second switch is turned on.

When assuming the switch drive start signal C _TR is high, and the first switch S ₁ is closed the third switch S ₃ is turned on, the second switch S ₂ is turned off, while the high level of the switch drive signal C _TR The main switch M is closed and turned on. At this time, the equivalent output current I _EQ is set to zero, that is, I _EQ =0. As described above, the AC input voltage V _{IN is passed} through the rectifier bridge 101, the input capacitor C _IN , the primary winding T ₁ , the main switch M, and the first sampling resistor R _S to ground. The current flowing through the main switch M rises linearly under the action of the exciting inductance of the primary winding T ₁ , and the voltage across the first sampling resistor R _S , that is, the current sampling signal I _sense also rises linearly. At this time, since the first switch S ₁ is turned on, the voltage across the capacitor C ₁ is the current sampling signal I _sense . That is to say, during this period of time, the voltage across the capacitor C ₁ rises linearly. When it rises to the set peak current I _PK , the switch drive signal C _TR becomes a low level. Accordingly, the first switch S ₁ and the third switch S ₃ are turned off, the second switch S ₂ is turned off; the main switch M is turned off. At this time, the equivalent output current I _EQ is the voltage across the capacitor C ₁ , that is, I _EQ =I _PK ×R _RS , where R _RS is the resistance value of the first sampling resistor R _S .

The waveforms of the switch drive signal C _TR , the current I _M flowing through the main switch M, the current I D flowing through the diode _D , the voltage V _{T3 of the} third winding T ₃ , and the equivalent output current I _EQ are as shown in FIG. 5 . .

As can be seen from Figure 5, the average value of the equivalent output current I _EQ in one switching cycle is

The average value I _{D (AVE)} of the current I _D flowing through the diode in one cycle is

Where T _ON is the closed on-time of the main switch M in one cycle, and T _OFF is the off-time of the main switch M in one cycle.

Obtained by the above equations (1) and (2),

It can be seen from equation (3) that when the resistance value R _{RS of the} first sampling resistor R _S is given, the average value of the equivalent output current I _{EQ and} the average value of the current I _D flowing through the diode D become Just proportional. Since the direct current flowing through the output capacitor C _O is zero, the average value of the current I _D flowing through the diode _D is equal to the average current flowing through the LED. Thus, the equivalent output current proportional to the average value of the average current flowing through the LED I _EQ, the equivalent output current I _EQ is the average current through the LED output that is the equivalent value of the current. The output current calculator 104 implements sampling of the primary side of the secondary side LED.

FIG. 6 shows an isolation conversion circuit 600 in accordance with one embodiment of the present invention. The circuit module of the isolation conversion circuit 600 and the same portion of the isolation conversion circuit 200 are given the same reference numerals. Unlike the isolation conversion circuit 200, the isolation conversion circuit 600 specifically illustrates an implementation structure of the controller 102. However, those skilled in the art will recognize that the circuit configuration of the controller 102 is not limited to the circuit configuration shown in FIG. As shown in FIG. 6, the controller 102 includes an error amplifier U _A having an input (inverting input) coupled to the output of the output current calculator 104 to receive an equivalent output provided by the output current calculator 104. The current I _EQ , the other input (non-inverting input) receives the reference signal R _EF to provide an error amplification signal according to the equivalent output current I _EQ and the reference signal R _EF , ie the set peak current I _PK to the comparator U _C Inverting input terminal; comparator U _C , an input terminal (inverting input terminal) coupled to the output end of the error amplifier U _A to receive the error amplification signal, and the other input end (in-phase input terminal) coupled a series coupling point of the first sampling resistor R _S and the main switch M to receive the current sampling signal I _sense to provide a comparison signal S _CMP to the logic circuit according to the error amplification signal and the current sampling signal I _sense ; the logic circuit receives at one end the comparison signal S _CMP, and the other end receiving a zero cross detection signal Z _DET, to provide a switch in accordance with the comparison signal S _CMP and the zero-cross detection signal Z _DET driving signal C _TR to control the main switch M is closed and is turned OFF. In this embodiment, the logic circuit is an RS flip-flop, and the set terminal R is coupled to the output end of the comparator U _C to receive the comparison signal S _CMP ; the reset end is coupled to the output end of the zero-cross detector 103 . To receive the zero-cross detection signal Z _DET ; its output terminal Q is coupled to the control terminal of the main switch M to provide the switch drive signal C _TR . In this embodiment, a compensation circuit Z _C is coupled between the output of the error amplifier U _A and the primary reference ground. In one embodiment, the compensation circuit Z _C is the capacitance of the compensation network may be, may be resistance, capacitance compensation network, the structure of those skilled in the art. For the sake of brevity, the circuit structure of the compensation circuit Z _C will not be described in detail herein.

As shown in FIG. 6, due to the coupling mode of the error amplifier U _A , the set peak current I _PK , that is, the error amplification signal is determined by the equivalent output current I _EQ and the reference signal R _EF . From equation (3), the equivalent output current I _EQ is proportional to the average current flowing through the LED, and the reference signal R _EF is a given signal. Therefore, the set peak current I _PK is the average current flowing through the LED. Decide. When the sampling current I _sense reaches the set peak current I _PK during the period in which the main switch M is turned on, the comparison signal S _CMP outputted by the comparator _goes high, thereby resetting the output of the RS flip-flop, and the switch driving signal C _TR It is reset to low to disconnect the main switch M. Therefore, the average current flowing through the LED determines the set peak current I _PK , that is, the time point at which the main switch M is controlled to be turned off. When the main switch M is turned off, when the zero-crossing detector detects that the voltage V _{T3 of the} third winding T ₃ is zero, the high-level zero-cross detection signal Z _DET is output, thereby setting the output of the meta-RS flip-flop , causing the switch drive signal C _TR to go high. Accordingly, the main open door M is closed and turned on, and the isolation conversion circuit 600 enters a new duty cycle.

FIG. 7 shows an isolation conversion circuit 700 in accordance with another embodiment of the present invention. The circuit module of the isolation conversion circuit 700 and the same portion of the isolation conversion circuit 400 are given the same reference numerals. For the sake of brevity, the coupling of the same parts will not be described in detail here. And isolation of different conversion circuit 400, in order to avoid output current calculator _{104. 1} C is the capacitance value of the capacitance is not large enough, the impedance matching can not be achieved, the isolation circuit 700 converting the output current of the capacitance C in the calculator 104 in practical applications A buffer U ₁ is coupled between ₁ and the second switch S ₂ . That is, the output current calculator 104 includes: a first switch S ₁ , one end coupled to the series coupling point of the first sampling resistor R _S and the main switch M; the first capacitor C ₁ coupled to the first switch S ₁ Between the one end and the primary side reference ground; the buffer U ₁ , the input end of which is coupled to the coupling point of the first switch S ₁ and the first capacitor C ₁ ; the second switch S ₂ , coupled to the buffer U ₁ The third switch S _{3 is} coupled between the other end of the second switch S ₂ and the ground. The control ends of the first switch S ₁ , the second switch S ₂ and the third switch S ₃ are coupled to the output end of the controller 102, and when the switch drive signal C _TR is at a high level, the first switch S ₁ and the third switch S ₃ is closed is turned on, turned off the second switch S _3; when the switch drive signal C _TR is low, the first switch S ₁ is turned off and the third switch S _3, S ₂ is closed the second switch is turned on. Those skilled in the art should appreciate that the operation of the isolation conversion circuit 700 is the same as that of the isolation conversion circuit 400. For the sake of brevity, it will not be described in detail herein.

FIG. 8 shows an isolation conversion circuit 800 in accordance with yet another embodiment of the present invention. The circuit module of the isolation conversion circuit 800 is similar to the isolation conversion circuit 200, and the same portions of the isolation conversion circuit 800 as the isolation conversion circuit 200 are given the same reference numerals. For the sake of brevity, the coupling of the same parts will not be described in detail here. The insulating converter circuit 200 except that the insulating converter circuit 800 will be omitted third winding T _3, instead, the insulating converter circuit 800 employs a zero-crossing detector capacitance C _2. And one end of the zero-crossing detecting capacitor C ₂ is coupled to the input end of the zero-crossing detector 103. The other end of the zero-crossing detecting capacitor C ₂ is coupled to the series coupling point of the main switch M and the primary winding T ₁ . When the main switch M is turned off, the current I _D flowing through the diode _D starts to fall from n × I _PK , and when it falls to zero, the magnetizing inductance of the primary winding T ₁ and the parasitic capacitance of the main switch M (not The illustration shows an oscillation. When the oscillation is zero crossing for the first time, the current flowing through the zero-cross detecting capacitor C ₂ is reversed, the zero-crossing detector 103 detects the reverse current, and outputs a high-level zero-crossing detection signal Z _DET , thereby causing the controller 102 The high level switch drive signal C _{TR is} output to turn the main switch M closed. The isolation converter circuit 800 enters a new duty cycle. The remaining working principle of the isolation conversion circuit 800 is the same as that of the isolation conversion circuit 200 described above, and is not described in detail herein.

Although the specific structure of the output current calculator 105 is not shown in the isolation conversion circuit 800 shown in FIG. 8, in one specific embodiment, the output current calculator 105 may be the structure shown in FIG. 4 or FIG. 7; In a specific embodiment, the compensation circuit Z _C as shown in FIG. 6 can also be added on the basis of the above.

Although the idea of the present invention has been described above with LED elements as driven components, those of ordinary skill in the art will appreciate that embodiments of the present invention are also applicable to other types of drive components, such as current sources.

The above disclosure is only intended to be a preferred embodiment or embodiment, and many modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims. The specific embodiments described herein are for illustrative purposes only, and various modifications and equivalents can be made by those skilled in the art in the spirit and scope of the invention. The scope of protection encompassed by the present invention is subject to the scope of the appended claims. All changes and modifications that come within the scope of the claims and their equivalents should be covered by the appended claims.

100‧‧‧Isolation conversion circuit

101‧‧‧Rectifier Bridge

102‧‧‧ Controller

103‧‧‧Zero cross detector

104‧‧‧Output current calculator

110‧‧‧Isolated feedback circuit

200‧‧‧Isolation conversion circuit

400‧‧‧Isolation conversion circuit

600‧‧‧Isolation conversion circuit

700‧‧‧Isolation conversion circuit

800‧‧‧Isolation conversion circuit

T‧‧‧Transformer

M‧‧‧ main switch

T ₁ ‧‧‧ primary winding

T ₂ ‧‧‧ secondary winding

T ₃ ‧‧‧third winding

S ₁ ‧‧‧first switch

S ₂ ‧‧‧second switch

S ₃ ‧‧‧third switch

C ₁ ‧‧‧first capacitor

U ₁ ‧‧‧buffer

U _A ‧‧‧Error Amplifier

U _C ‧‧‧ comparator

Z _C ‧‧‧compensation circuit

FIG. 1 shows a conventional isolation conversion circuit 100.

FIG. 2 illustrates an isolation conversion circuit 200 in accordance with one embodiment of the present invention.

Figure 3 shows a flow chart 300 of the operation of an output current calculator in accordance with the present invention.

4 illustrates an isolation conversion circuit 400 employing the method of calculating the secondary side output current of the isolation conversion circuit of FIG. 3, in accordance with one embodiment of the present invention.

5 shows the waveforms of the switching drive signal, the current flowing through the main switch, the current flowing through the diode, the voltage of the third winding, and the equivalent output current in the isolation conversion circuit 400 shown in FIG.

FIG. 6 illustrates an isolation conversion circuit 600 that specifically illustrates an implementation of a controller in accordance with one embodiment of the present invention.

FIG. 7 shows an isolation conversion circuit 700 in accordance with another embodiment of the present invention.

FIG. 8 shows an isolation conversion circuit 800 in accordance with yet another embodiment of the present invention.

101. . . Rectifier bridge

102. . . Controller

103. . . Zero crossing detector

104. . . Output current calculator

200. . . Isolated conversion circuit

Claims (18)

An isolation conversion circuit includes: a transformer including a primary winding, a secondary winding, and a third winding, the primary winding is configured to receive an input signal of the isolation conversion circuit, and the secondary winding is configured to provide a driving signal to the a driving component; a main switch coupled to the primary winding, turned on and off according to the switch driving signal; and an output current calculator that calculates a flow according to a current flowing through the main switch and the switch driving signal during the main switch being turned on An equivalent output current of the driven component; a zero-crossing detector, providing a zero-crossing detection signal according to a voltage across the third winding; and a controller, according to the equivalent output current, a zero-crossing detection signal, and the main switch being turned on The current flowing through the main switch and a reference signal are provided to provide the switch drive signal. The circuit of claim 1, wherein the output current calculator comprises: a first switch, one end receiving a current flowing through the main switch; and a first capacitor coupled to the other end of the first switch The second switch is coupled to the series coupling point of the first switch and the first capacitor; the third switch is coupled to the other end of the second switch and the primary side reference ground between; The first switch, the second switch, and the third switch are controlled to be turned on and off by the switch driving signal; the output current calculator provides and the series coupling point of the second switch and the third switch The current corresponding to the output current. The circuit of claim 2, wherein the output current calculator further comprises a buffer coupled between the series coupling point of the first switch and the first capacitor and the second switch. The circuit of claim 2, wherein when the switch drive signal is at a high level, the first switch and the third switch are controlled to be turned on, and the second switch is controlled to be turned off; when the switch drive signal When it is low, the first switch and the third switch are controlled to be turned off, and the second switch is controlled to be turned on. The circuit of claim 1, wherein the controller comprises: an error amplifier, providing an error amplification signal according to the equivalent output current and the reference signal; and comparing, according to the error amplification signal, the main switch is turned on The current flowing through the main switch provides a comparison signal; the logic circuit provides the switch drive signal based on the comparison signal and the zero-cross detection signal. The circuit of claim 1, wherein the controller further comprises a compensation circuit coupled between the error amplifier and the primary side reference ground. An isolation conversion circuit comprising: a transformer comprising a primary winding and a secondary winding, the primary winding for receiving an input signal of the isolation conversion circuit, the secondary winding for providing a driving signal to the driven component; and a main switch coupled to the original The side winding is turned on and off according to the switch driving signal; the zero cross detecting capacitor is coupled to the series coupling point of the primary winding and the main switch, and the other end is coupled to the input end of the zero crossing detector; a current calculator that calculates an equivalent output current flowing through the driven component according to a current flowing through the main switch during the conduction of the main switch and the switch driving signal; the zero-crossing detector according to the zero-crossing detecting capacitor flowing through The current provides a zero-cross detection signal; the controller provides the switch drive signal based on the equivalent output current, the zero-cross detection signal, the current flowing through the main switch during the on-time of the main switch, and a reference signal. The circuit of claim 7, wherein the output current calculator comprises: a first switch, one end receiving a current flowing through the main switch; and a first capacitor coupled to the other end of the first switch The second switch is coupled to the series coupling point of the first switch and the first capacitor; the third switch is coupled to the other end of the second switch and the primary side reference ground between; The output current calculator provides a current corresponding to the equivalent output current at a series coupling point of the second switch and the third switch. The circuit of claim 8 wherein the output current calculator further comprises a buffer coupled between the series coupling point of the first switch and the first capacitor and the second switch. The circuit of claim 8, wherein when the switch drive signal is at a high level, the first switch and the third switch are controlled to be turned on, and the second switch is controlled to be turned off; when the switch drive signal When it is low, the first switch and the third switch are controlled to be turned off, and the second switch is controlled to be turned on. The circuit of claim 7, wherein the controller comprises: an error amplifier, providing an error amplification signal according to the equivalent output current and the reference signal; and comparing, according to the error amplification signal, the main switch is turned on The current flowing through the main switch provides a comparison signal; the logic circuit provides the switch drive signal based on the comparison signal and the zero-cross detection signal. The circuit of claim 7, wherein the controller further comprises a compensation circuit coupled between the error amplifier and the primary side reference ground. A luminaire using the circuit described in claim 1 or claim 7 of the patent application. A method for an isolated conversion circuit, the circuit comprising: a transformer comprising a primary winding, a secondary winding and a third winding, the primary winding receiving an input signal of the isolation converter circuit, the secondary winding for providing a driving signal to the driven component; and a main switch, Coupling to the primary winding, being turned on and off according to the switch driving signal, the method comprising the steps of: calculating a current flowing through the driven component according to a current flowing through the main switch during the conduction of the main switch and the switch driving signal An equivalent output current; providing a zero crossing detection signal according to the voltage across the third winding; providing the equivalent output current, the zero crossing detection signal, the current flowing through the main switch during the conduction of the main switch, and a reference signal The switch drives the signal. The method of claim 14, wherein the main switch of the primary winding of the isolation conversion circuit is turned on and off periodically. The method of claim 15, wherein the current flowing through the main switch is sampled during a time interval in which the main switch is turned on, and the equivalent value is set to zero. The method of claim 16, wherein a peak current flowing through the main switch is maintained during a time interval in which the main switch is turned off, and the peak current is taken as a time interval during which the main switch is turned off. The equivalent value. The method of claim 14, further comprising determining a conduction state of the main switch.