TWI506926B - Dc/dc controller and driving controller thereof - Google Patents

Description

DC/DC converter and its drive controller

The invention relates to a power conversion circuit, in particular to a DC/DC converter, a drive controller for controlling a transformer.

The display system usually includes a lighting module and a control module. The lighting module includes one or more light sources, for example, a plurality of sets of light emitting diode (LED) chains. The control module typically includes a microcontroller, an audio processor, and a video processor. The control module controls the activation/deactivation and brightness of the lighting module and processes the audio and video signals. Lighting modules and control modules may have different power requirements. Therefore, the input AC voltage needs to be converted into the first DC voltage and the second DC voltage has respectively supplied power to the lighting module and the control module.

FIG. 1 shows a schematic diagram of a conventional display system 100. The AC/DC converter 104 receives an AC voltage from the AC power source 102 and outputs a DC voltage VIN. The primary coil 106 of the transformer 130 receives a DC voltage VIN, produces an output voltage VOUT1 at the first secondary coil 110, and produces an output voltage VOUT2 at the second secondary coil 108. The output voltage VOUT1 supplies power to the control module 128. Control module 128 includes a microcontroller, a video processor, and an audio processor. The output voltage VOUT2 supplies power to the lighting module 126. The lighting module 126 includes a plurality of sets of LED strings. The control module 128 generates an ON/OFF signal to activate or deactivate the illumination module 126, and also generates a DIM signal to adjust the brightness of the illumination module 126. The error amplifier 118 monitors the output voltage VOUT1 through the voltage divider 120 and controls the optocoupler 116 to generate a feedback signal FB indicative of the output voltage VOUT1. The DC/DC controller 114 receives the feedback signal FB And generating a pulse signal to control the switch 112 connected in series with the primary coil 106, thereby controlling the power transmitted from the primary coil 106 to the first secondary coil 110, and adjusting the output voltage VOUT1 to the first voltage value to meet the power demand of the control module 128. . While controlling the switch 112, the output voltage VOUT2 also changes. A power converter (eg, boost converter 122) coupled between the second secondary coil 108 and the illumination module 126 adjusts the output voltage VOUT2 to a second voltage value to meet the power demand of the lighting module 126. Therefore, in order to generate the output voltage VOUT2 having different voltage values with the output voltage VOUT1, an additional power converter (for example, the boost converter 122) is required, thus increasing the manufacturing cost of the system.

2 is a schematic diagram of another conventional display system 200. Elements in Figure 2 that are numbered the same as in Figure 1 have similar functions. Display system 200 includes a first transformer 230 and a second transformer 232. The first transformer 230 generates a first output voltage VOUT1 to power the control module 128. The second transformer 232 generates a second output voltage VOUT2 to power the lighting module 126. The first DC/DC controller 214 controls the first switch 204 in series with the primary winding of the first transformer 230 according to the feedback signal FB1 generated by the first optical coupler 236 to adjust the first output voltage VOUT1. The second DC/DC controller 216 controls the second switch 202 in series with the primary winding of the second transformer 232 according to the feedback signal FB2 generated by the second optical coupler 234 to adjust the second output voltage VOUT2. Therefore, display system 200 requires the use of additional second DC/DC controller 216, second transformer 232, and second optocoupler 234, thus increasing the manufacturing cost of the system.

It is an object of the present invention to provide a DC/DC converter comprising: a transformer comprising a primary coil, a first secondary coil and a second secondary coil, the primary coil being coupled to a power source, the first secondary The coil provides a first output voltage to a first load, the second secondary coil provides a second output voltage to a second load; a switch controller coupled to the primary coil to control coupling with the primary coil a first switch for controlling an input power received by the primary coil, and adjusting the first output voltage according to a power demand of the first load; and a driving controller coupled to the second secondary coil to generate A pulse width modulation signal alternately turns on and off a second switch coupled to the second secondary coil, and adjusts the second output voltage according to a power demand of the second load.

The present invention also provides a drive controller for controlling a first output voltage output from a transformer to a load, comprising: a synchronization end point, receiving a synchronization signal from a first secondary winding of the transformer, indicating a switch control An operating frequency of the device; a voltage monitoring terminal receiving a voltage monitoring signal indicative of the output voltage; at least one current monitoring terminal receiving a current monitoring signal indicative of at least one current flowing through the load; and a driving end And generating a pulse width modulation signal according to the synchronization signal, the voltage monitoring signal, and the current monitoring signal to adjust the output voltage, and synchronizing an operating frequency of the driving controller with the operating frequency of the switch controller The drive controller is coupled to a second secondary coil of the transformer.

A detailed description of the embodiments of the present invention will be given below. Although this hair The invention will be explained in conjunction with the embodiments, but it should be understood that this is not intended to limit the invention to these embodiments. Rather, the invention is to cover various modifications, equivalents, and equivalents of the invention as defined by the scope of the appended claims.

In addition, in the following detailed description of the embodiments of the invention However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail in order to facilitate the invention.

3 is a circuit diagram of a display system 300 in accordance with an embodiment of the present invention. The display system 300 includes an AC/DC converter (such as a bridge rectifier 304) that converts an AC voltage from the AC power source 302 into a DC voltage VIN, and a DC/DC converter 301 that converts the DC voltage VIN into a first output. Voltage VOUT1 and second output voltage VOUT2. The DC/DC converter 301 includes a transformer 332 coupled to a bridge rectifier 304. The transformer 332 includes a primary coil LP, a secondary coil L1, and a secondary coil L2. The DC/DC converter 301 further includes a switch Q1 connected in series with the primary coil LP, a switch Q2 connected in series with the secondary coil L2, and a switch coupled to the switch Q1 and controlling the input power received by the primary coil LP to adjust the output voltage VOUT1. The DC controller 314, and the driver controller 324, pass the control switch Q2 to adjust the output voltage VOUT2. In the example of FIG. 3, switch Q1 is an N-channel metal oxide semiconductor field effect transistor (NMOSFET), and switch Q2 is a P-channel metal oxide semiconductor field effect transistor (PMOSFET).

The primary coil LP of the transformer 332 receives the DC voltage VIN, the secondary line Loops L1 and L2 produce an output voltage VOUT1 output voltage and VOUT2, respectively. The output voltage VOUT1 is applied to the control module 328. In an embodiment, control module 328 includes a microcontroller, a video processor, and an audio processor. The microcontroller controls the video processor and audio processor based on the user's input to adjust the video output and audio output. The output voltage VOUT2 is applied to the illumination module 326. The lighting module 326 includes one or more light sources, such as multiple sets of LED strings. The control module 328 generates an ON/OFF signal to activate or deactivate the illumination module 326, and generates a DIM signal to adjust the brightness of the illumination module 326. The error amplifier 318 monitors the output voltage VOUT1 through a voltage monitor (eg, voltage divider 320) coupled to the secondary coil L1, and controls the optical coupler 316 to generate a feedback signal FB indicative of VOUT1. The DC/DC controller 314 receives the feedback signal FB from the optical coupler 316 and the monitoring signal LPSEN provided by the current monitor 330 in series with the switch Q1, generates a control signal DRV1 to control the switch Q1, and adjusts the output voltage VOUT1 to the first Voltage. In an embodiment, the control signal DRV1 is a pulse width modulation signal (eg, a pulse width modulation signal). The monitor signal LPSEN indicates the current flowing through the primary coil LP.

The driver controller 324 generates monitoring signals ISEN_1, ISEN_2, ..., ISEN_N indicating the current flowing through the LED strings in the illumination module 326, and receives a monitoring signal VSEN indicating the output voltage VOUT2 generated by the secondary coil L2. In an embodiment, the monitor signal VSEN is provided by a voltage monitor (eg, voltage divider 338) coupled to the secondary coil L2. The driver controller 324 generates a control signal DRV2 based on the monitor signals ISEN_1, ISEN_2, . . . , ISEN_N and the monitor signal VSEN to control the switch Q2, thereby adjusting the output voltage VOUT2 to the second voltage. In an embodiment, the control signal DRV2 is a pulse width modulation signal. In addition, the drive controller 324 is also rooted The activation, shutdown, and brightness of the illumination module 326 are controlled based on the ON/OFF signals and DIM signals generated by the control module 328.

4 is a circuit diagram of the driver controller 324 shown in FIG. In the example of FIG. 4, the driver controller 324 includes a current adjustment unit 404, a reference signal generator 410, an error amplifier 408, a ramp signal generator 412, a comparator 406, and an inverting buffer 402. Figure 4 will be described in conjunction with Figure 3.

In one embodiment, the current adjustment unit 404 balances the currents of the plurality of sets of LED strings in the illumination module 326 such that the current flowing through the LED strings of the LED strings is substantially equal to the target current value. Here, "substantially equal to the target current value" means that the current of each LED string is limited to a certain range, so that each LED string produces a light output having a uniform brightness.

In addition, the current adjustment unit 404 adjusts the output voltage VOUT2 to meet the power demand of the lighting module 326. In particular, current adjustment unit 404 adjusts output voltage VOUT2 such that the voltage drop across each set of LED strings is sufficient to turn the LED string on and produce a current that is nearly equal to the target current value. The current adjustment unit 404 generates the monitor signals ISEN_1, ISEN_2, . . . , ISEN_N, and controls the reference signal generator 410 to generate the reference signal ADJ according to the power demand of the illumination module 326. In an embodiment, the current adjustment unit 404 controls the reference signal generator 410 to increase the reference signal ADJ to increase the output voltage VOUT2, and vice versa.

The error amplifier 408 receives the reference signal ADJ and the monitor signal VSEN indicating the output voltage VOUT2, and compares the reference signal ADJ with the monitor signal VSEN to generate an error signal ER. In an embodiment, if the reference signal ADJ is increased, the error amplifier 408 increases the error signal ER accordingly. Comparators 406 compares the error signal ER with the ramp signal RAMP generated by the ramp signal generator 412 to generate the signal DRV2B. In an embodiment, the inverting buffer 402 inverts the signal DRV2B to generate a control signal DRV2, and the control signal DRV2 is used to control the switch Q2 in series with the secondary coil L2 (eg, a P-channel metal oxide semiconductor field effect transistor) , PMOSFET). In the example of FIG. 4, the signal DRV2B and the control signal DRV2 are pulse width modulation signals. If the control signal DRV2 is in the first state (eg, logic 0), the switch Q2 is turned "on". If the control signal DRV2 is in the second state (eg, logic 1), the switch Q2 is turned off. The duty cycle of the control signal DRV2 is determined by the error signal ER. In one embodiment, if the error signal ER is increased, the comparator 406 increases the duty cycle of the signal DRV2B such that the on period of the switch Q2 increases. Therefore, the average current flowing through the secondary coil L2 increases, and the output voltage VOUT2 also increases.

FIG. 5 is a signal waveform diagram of the display system 300 shown in FIG. Figure 5 will be described in conjunction with Figure 3. 5 shows the control signal DRV1 generated by the DC/DC controller 314, the state of the switch Q1, the current I _LP flowing through the primary coil LP, the current I L1 flowing through the secondary coil _L1 , and the control generated by the driver controller 324. Signal DRV2 and current I _L2 flowing through secondary coil _L2 .

The DC/DC controller 314 receives the monitor signal LPSEN indicating the current I _LP flowing through the primary coil LP, and generates a control signal DRV1 to control the switch Q1. If the control signal DRV1 is in the first state (eg, logic 1), the switch Q1 is turned on, and the current I _LP flowing through the primary coil LP is increased. When the switch Q1 is turned on, since the diode D1 connected to the secondary coil L1 and the diode D2 connected to the secondary coil L2 are both reverse-biased, no current flows through the secondary coils L1 and L2. When the voltage of the monitoring signal LPSEN increases to a preset voltage value, indicating that the current I _LP increases to the preset current value IPK, the DC/DC controller 314 changes the control signal DRV1 to the second state (eg, logic 0) to be off. Turn on the switch Q1. When switch Q1 is turned off, current I _LP decreases. The current I _L1 flowing through the secondary coil _L1 and the current I _L2 flowing through the secondary coil _L2 are both reduced, and both are regulated by the switch Q2. The conduction state of the switch Q2 is determined by the control signal DRV2. It is assumed that the number of turns of the primary coil LP is NP, the number of turns of the secondary coil L1 is N1, and the number of turns of the secondary coil L2 is N2. If the control signal DRV2 is in the first state, the switch Q2 is turned on, and the current I _L1 flows from the secondary coil L1 through the diode D1 to the control module 328; the current I _L2 flows from the ground through the switch Q2 and the secondary coil L2. The diode D2 flows to the illumination module 326. When switch Q2 is turned on, I _L1 and I _L2 can be expressed as: NP*I _LP =N1*I _L1 +N2*I _L2 (1)

If the control signal DRV2 is in the second state, the switch Q2 is turned off and I _L2 remains off. When switch Q2 is open, I _L1 can be expressed as: NP* I _LP =N1* I _L1 (2)

In one embodiment, transformer 332 operates in a fixed frequency mode with control signal DRV1 having a fixed frequency and an adjustable duty cycle. In another embodiment, the frequency and duty cycle of the control signal DRV1 are both adjustable.

As described above, the DC/DC controller 314 adjusts the output voltage VOUT1 by controlling the input power received by the primary coil LP. Specifically, the DC/DC controller 314 controls the switch Q1 in series with the primary coil LP based on the feedback signal FB and the monitor signal LPSEN. The feedback signal FB indicates the output voltage VOUT1. The monitor signal LPSEN indicates the current I _LP flowing through the primary coil _LP . The driver controller 324 controls the switch Q2 in series with the secondary coil L2 according to the monitor signals ISEN_1, ISEN_2, ..., ISEN_N and the monitor signal VSEN to adjust the output voltage VOUT2. The monitor signals ISEN_1, ISEN_2, ..., ISEN_N indicate the current flowing through each of the LED strings in the illumination module 326. The monitor signal VSEN indicates the output voltage VOUT2. Therefore, the boost converter 122 in the conventional display system 100 or the DC/DC controller 216, the transformer 232, and the optical coupler 234 in the conventional display system 200 can be eliminated, thereby saving cost.

6 is a circuit diagram of a display system 600 in accordance with another embodiment of the present invention. Elements in Figure 6 that are numbered the same as in Figure 3 have similar functions. FIG. 7 is a signal waveform diagram of the display system 600 shown in FIG. Figure 6 will be described in conjunction with Figure 7.

Display system 600 includes an AC/DC converter (eg, bridge rectifier 304) that converts an AC voltage from AC power source 302 to a DC voltage VIN, and a DC/DC converter 601 that converts DC voltage VIN to a first output. Voltage VOUT1 and second output voltage VOUT2. The DC/DC converter 601 includes a transformer 632 that is coupled to a bridge rectifier 304. The transformer 632 includes a primary coil LP, a secondary coil L1, and a secondary coil L2. In one embodiment, the secondary coil L1 has a tap point that is connected to ground. The secondary coil L2 also has a tap point that is connected to ground via switch Q2. The DC/DC converter 601 further includes a switch Q11 coupled between the bridge rectifier 304 and the primary coil LP and a switch Q10 coupled between the primary coil LP and the ground, and a DC/DC controller 614 and a driver controller 324. The DC/DC controller 614 is coupled to the switches Q10 and Q11, and adjusts the output voltage VOUT1 by controlling the input power received by the primary coil LP. The driver controller 324 is coupled to the switch Q2 and adjusts the output voltage VOUT2 through the control switch Q2.

In the example of Figure 6, switches Q10 and Q11 are NMOSFETs, controlled by control signals DRV10 and DRV11, respectively. The DC/DC controller 614 generates control signals DRV10 and DRV11 based on the feedback signal FB indicating the output voltage VOUT1 and the monitoring signal LPSEN indicating the current I _LP flowing through the primary coil LP. A current monitor 330 in series with the primary coil LP generates a monitor signal LPSEN. The DC/DC controller 614 can determine whether an overcurrent condition has occurred based on the monitoring signal LPSEN.

In the example of Figure 6, switch Q2 is a PMOSFET controlled by control signal DRV2. The driver controller 324 generates a control signal DRV2 based on the monitor signals ISEN_1, ISEN_2, ..., ISEN_N, and VSEN. In one embodiment, control signal DRV2 is a pulse width modulated signal. If the control signal DRV2 is in the first state, the switch Q2 is turned on. If the control signal DRV2 is in the second state, the switch Q2 is turned off. The monitor signal VSEN indicates the output voltage VOUT2. The monitor signals ISEN_1, ISEN_2, ..., ISEN_N indicate the current flowing through each of the LED strings in the illumination module 326.

The DC/DC controller 614 generates control signals DRV10 and DRV11 to alternately turn on the switches Q10 and Q11 to control the input power received by the transformer 632 primary coil LP. In an embodiment, the control signals DRV10 and DRV11 are pulse signals having a predetermined duty cycle and an adjustable frequency. The DC/DC controller 614 determines the frequencies of the control signals DRV10 and DRV11 based on the power requirements of the lighting module 326. When the control signal DRV10 is in the first state (eg, logic 1), the switch Q10 is turned on. When the control signal DRV10 is in the second state (eg, logic 0), the switch Q10 is turned off. When the control signal DRV11 is in the first state (for example, logic 1), the switch Q11 is turned on. When the control signal DRV11 is in the second state (eg, logic 0), the switch Q11 is turned off.

In an embodiment, DC/DC controller 614 turns on switch Q11 and keeps switch Q10 off at time T1. From time T1 to T2, switch Q11 is turned on, switch Q10 is turned off, current I _LP flows from bridge rectifier 304 through switch Q11 and primary coil LP, and an energy storage element (eg, capacitor C1) coupled to primary coil LP Charging. At time T2, the DC/DC controller 614 turns off the switch Q11 and keeps the switch Q10 open. From time T2 to T3, switches Q10 and Q11 are both off, and current I _LP flows from ground through the body diode of switch Q10 and primary coil LP. At time T3, the DC/DC controller 614 turns on the switch Q10 and keeps the switch Q11 open. From time T3 to T4, switch Q10 is turned on, switch Q11 is turned off, and current I _LP flows from ground through switch Q10 and primary coil LP until current I _{LP is} reduced to a reference value, for example, zero. After the current I _{LP is} reduced to zero, the capacitor C1 is discharged, and the current I _LP flows from the capacitor C1 through the primary coil LP and the switch Q10 to ground. At time T4, the DC/DC controller 614 turns off the switch Q10. From time T4 to T5, switches Q10 and Q11 are both open, and current I _LP flows from capacitor C1 through primary coil LP, body diode of switch Q11, and bridge rectifier 304 to ground. At time T5, the DC/DC controller 614 turns on the switch Q11 again. Therefore, the power transmitted from the bridge rectifier 304 to the primary coil LP can be controlled by the control switches Q10 and Q11.

The secondary coil L1 generates a current I _L1 . The output voltage VOUT1 is proportional to the average of the current I _L1 . The DC/DC controller 614 adjusts the average value of the current I _L1 by adjusting the frequencies of the control signals DRV10 and DRV11. In one embodiment, if the feedback signal FB generated by the optocoupler 316 indicates that the output voltage VOUT1 is greater than the desired voltage value of the control module 328, the DC/DC controller 614 increases the frequency of the control signals DRV10 and DRV11 to reduce the current. The average value of I _L1 , the output voltage VOUT1 also decreases. Similarly, if the output voltage VOUT1 is less than the desired voltage value of the control module 328, the DC/DC controller 614 decreases the frequency of the control signals DRV10 and DRV11 to increase the average value of the current I _L1 , and the output voltage VOUT1 also increases. Big. Therefore, the output voltage VOUT1 is adjusted to a voltage value that satisfies the power demand of the control module 328.

If the switch Q2 is turned on, the secondary coil L2 generates a current I _L2, the absolute value is proportional to the current I _L2 of the current I _LP. When switch Q2 is turned on, current I _L2 flows from ground through a portion of switch Q2 and secondary coil L2 to illumination module 326. When switch Q2 is turned off, current I _L2 remains off. Therefore, the average value of the current I _L2 is proportional to the on period of the switch Q2 and is determined by the control signal DRV2. The output voltage VOUT2 is proportional to the average of the current I _L2 . The driver controller 324 adjusts the duty cycle of the control signal DRV2 according to the monitoring signals ISEN_1, ISEN_2, . . . , ISEN_N and VSEN, so that the output voltage VOUT2 is adjusted to a voltage value capable of satisfying the power demand of the lighting module 326.

Assuming that the number of turns of the primary coil LP is NP, the absolute value of the current I _LP is I' _LP . The tap point of the secondary coil L1 divides the secondary coil L1 into a first portion and a second portion, the first portion having a number of turns of N11 and the second portion having a number of turns of N12. The tap point of the secondary coil L2 divides the secondary coil L2 into a first portion and a second portion, the first portion having a number of turns of N21 and the second portion having a number of turns of N22. The current I _L1 flows through the inductor L6 to the control module 328, and the current I _L2 flows through the inductor L7 to the illumination module 326. If the control signal DRV2 is in the first state, the switch Q2 is turned on, and the current I _{LP is} in the positive half cycle, I _L1 , I _L2 can be expressed as: NP * I _LP = N11 * I _L1 + N21 * I _L2 (3)

If the control signal DRV2 is in the first state, the switch Q2 is turned on, and the current I _{LP is} in the negative half cycle, I _L1 , I _L2 can be expressed as: NP * I' _LP = N12 * I _L1 + N22 * I _L2 (4 )

If the control signal DRV2 is in the second state, the switch Q2 is turned off and the current I _{L2 is} kept off. When switch Q2 is open and current I _{LP is} in the positive half cycle, I _L1 can be expressed as: NP* I _LP =N11* I _L1 (5)

When switch Q2 is open and current I _{LP is} in the negative half cycle, I _L1 can be expressed as: NP* I' _LP = N12* I _L1 (6)

8 is a flow chart 800 of a method of controlling a transformer to generate a plurality of output voltages in accordance with an embodiment of the present invention. Figure 8 will be described in conjunction with Figures 3 and 6.

In step 802, a first secondary winding L1 of a transformer (e.g., transformer 332 shown in FIG. 3 or transformer 632 shown in FIG. 6) produces a first output voltage. In step 804, the second winding L2 of the transformer produces a second output voltage. In step 806, the first output voltage is adjusted by controlling the input power received by the transformer primary coil LP.

In step 808, a pulse width modulation signal is generated (e.g., using driver controller 324 shown in FIG. 3 or driver controller 324 shown in FIG. 6). In step 810, the pulse width modulation signal alternately turns on and off the current flowing through the second secondary coil L2, thereby adjusting the second output voltage. For example, a switch coupled to the second secondary winding L2 (for example, the switch Q2 shown in FIG. 3 or the switch Q2 shown in FIG. 6) is controlled by a pulse width modulation signal to adjust the second output voltage. If the pulse width modulation signal is in the first state, the switch is turned on, and current flows to the load through the second secondary coil L2. If the pulse width modulation signal is in the second state, the switch is turned off, and the current flowing through the second secondary coil L2 is turned off.

As described above, the present invention provides DC/DC conversion with multiple outputs Device. The DC/DC converter adjusts the input power received by the primary coil of the transformer to adjust the first output voltage generated by the first secondary winding of the transformer, and adjusts the transformer for the second time by controlling a switch coupled to the second secondary coil of the transformer. The second output voltage produced by the stage coil. The DC/DC converter provided by the present invention can be applied to a display system. Additional components (e.g., boost converters or second transformers) for adjusting the second output voltage in the prior art may be omitted, thereby saving cost.

FIG. 9 is a circuit diagram of a display system 900 in accordance with yet another embodiment of the present invention. Display system 900 includes an AC/DC converter (eg, bridge rectifier 904) and a DC/DC converter 901. Among them, the AC/DC converter is used to convert the AC voltage from the AC power source 902 into a DC voltage VIN. The DC/DC converter 901 is configured to convert the DC voltage VIN into a first output voltage VOUT1 and a second output voltage VOUT2 to drive the first load and the second load, respectively. In one embodiment, DC/DC converter 901 includes a transformer 932 coupled to bridge rectifier 904, a switch controller (eg, DC/DC controller 914), and a drive controller 924. The transformer 932 includes a primary coil LP, a secondary coil L1, and a secondary coil L2 coupled to an alternating current power source 902. Wherein, the secondary coil L1 generates a first output voltage VOUT1 applied to the first load (eg, the control module 928), and the secondary coil L2 generates a second output voltage applied to the second load (eg, the illumination module 926) VOUT2. In an embodiment, the transformer 932 further includes an auxiliary coil LA for providing a supply voltage VDD to the DC/DC controller 914. The DC/DC controller 914 is coupled to the primary coil LP for controlling the switch Q1 coupled to the primary coil to control the input power received by the primary coil LP and to adjust the first output voltage VOUT1 according to the power demand of the control module 928. . Drive control The 924 is coupled to the secondary coil L2 for generating a pulse width modulation signal for alternately opening and conducting the switch Q3 in series with the secondary coil L2, and adjusting the second according to the power demand of the lighting module 926. Output voltage VOUT2.

In the embodiment shown in FIG. 9, switch Q1 is an N-channel metal oxide semiconductor field effect transistor (NMOSFET), and switch Q3 is a P-channel metal oxide semiconductor field effect transistor (PMOSFET).

In the embodiment shown in Figure 9, switch Q3 receives a first output voltage VOUT1 from secondary coil L1. When the gate-source voltage Vsg of the switch Q3 is greater than a threshold, the switch Q3 is turned on. In the embodiment shown in FIG. 9, switch Q3 is disposed external to drive controller 924. Alternatively, the switch Q3 can also be disposed inside the drive controller 924. The DC/DC converter 901 further includes a transient voltage suppressor (eg, diode D3) coupled between the source and the drain of the switch Q3 as an overvoltage protection of the DC/DC converter 901. The leakage caused by the Leakage inductance of the diode D3 dispersion transformer 932 and the parasitic inductance on the printed circuit board (PCB) trace. When the transient voltage of the DC/DC converter 901 exceeds a preset level, the diode D3 is broken down to avoid an overvoltage condition of the DC/DC converter 901.

In operation, primary coil LP of transformer 932 receives DC voltage VIN, and first output voltage VOUT1 and second output voltage VOUT2 are generated at secondary windings L1 and L2, respectively. In the embodiment shown in FIG. 9, the first output voltage VOUT1 is applied to the control module 928, wherein the control module 928 includes a microcontroller, a video processor, and an audio processor. The microcontroller can control the video processor and the audio processor, for example, to adjust the output of the video and audio based on the user's input. The second output voltage VOUT2 is applied to the illumination module 926, wherein the illumination module includes a plurality of light sources, for example, multiple sets of LEDs string. The control module 928 generates an ON/OFF signal to turn the illumination module 926 on or off, and also generates a dimming signal DIM to adjust the brightness of the illumination module 926.

The DC/DC controller 914 is coupled between the optical coupler 916 and the primary coil LP for receiving a feedback signal FB indicating a target adjustment voltage of the first output voltage VOUT1 and indicating a current I _LP flowing through the primary coil LP. A monitoring signal LPSEN. The DC/DC controller 914 adjusts the first output voltage VOUT1 according to the feedback signal FB and the monitor signal LPSEN. In one embodiment, the DC/DC controller 914 is operative to generate a control signal DRV1 (eg, a pulse width modulation (PWM) signal) to alternately turn the switch Q1 on and off, and to pass the responsibility of adjusting the control signal DRV1. The first output voltage VOUT1 is adjusted during the cycle. When the control signal DRV1 is in the first state (eg, the logic 1 state), the switch Q1 is turned on, and the current I _LP flows through the primary coil LP. Since the diode D1 connected to the secondary coil L1 and the diode D2 connected to the secondary coil L2 are both reverse biased, no current flows through the secondary coils L1 and L2. When the control signal DRV1 is in the second state (for example, the logic 0 state), the switch Q1 is turned off, since both the diode D1 and the diode D2 are forward biased, the current I _L1 flows through the secondary coil L1, and the current I _L2 flows through the secondary coil L2.

In one embodiment, when the current flowing through the optocoupler 916 (eg, the feedback signal FB) is greater than a predetermined current, the actual first output voltage VOUT1 is indicated to be higher than the target regulated voltage of the first output voltage VOUT1. The DC/DC controller 914 reduces the preset current peak IPK of the current I _LP through the primary coil LP. When the voltage of the monitor signal LPSEN rises to a preset voltage, the indication current I _LP reaches the preset current peak IPK. The DC/DC controller 914 generates a control signal DRV1 in a second state (eg, logic 0) to turn off the switch Q1. Similarly, when the actual first output voltage VOUT1 is lower than the target regulated voltage of the first output voltage VOUT1, the DC/DC controller 914 raises the duty cycle of the control signal DRV1. Therefore, the DC/DC controller 914 adjusts the first output voltage VOUT1 to the target regulated voltage.

In an embodiment, the endpoints of the drive controller 924 include ISEN, OVP, VP, COMP, TS, BLON, PWM, and GATE, but are not limited thereto. In the embodiment shown in FIG. 9, a plurality of current monitoring endpoints are provided for respectively receiving current monitoring signals ISEN_1, ISEN_2 ... ISEN_N indicative of current flowing through respective LED strings in illumination module 926. The voltage monitoring endpoint OVP receives a voltage monitoring signal VSEN indicative of a second output voltage VOUT2 from a voltage monitor (eg, a voltage divider 938 coupled to the secondary coil L2). The endpoint VR receives a feedback signal FB indicative of the first output voltage VOUT1 from a voltage monitor (eg, a voltage divider 920 coupled to the secondary coil L1). In one embodiment, the drive controller 924 reduces the input power of the primary coil LP when the voltage VFB of the feedback signal is greater than the target regulation voltage, or when the voltage VSEN of the voltage monitoring signal is greater than the preset safety voltage. Specifically, when the compensation signal VCOMP is pulled low to zero, the current flowing through the optical coupler 916 (eg, the feedback signal FB) is increased to a maximum value. Therefore, the DC/DC controller 914 reduces the duty cycle of the control signal DRV1 to prevent an overvoltage condition of the lighting module 926 and the control module 928 from occurring. The driving terminal GATE generates a control signal DRV3 according to the current monitoring signals ISEN_1, ISEN_2, ... ISEN_N and the voltage monitoring signal VSEN, and controls the switch Q3 to adjust the second output voltage VOUT2 to the target voltage. In one embodiment, control signal DRV3 is a pulse width modulated signal (eg, a PWM signal). If the control signal DRV3 is in the first state (eg, logic 0), the current flowing through the secondary coil L2 is turned on. If The control signal DRV3 is in the second state (eg, logic 1), shutting off the current flowing through the secondary coil L2.

In the embodiment shown in FIG. 9, the sync endpoint TS receives the sync signal SYNC from the secondary coil L2, indicating the operating frequency of the DC/DC controller 914. The drive terminal GATE generates a control signal DRV3 based on the synchronization signal SYNE, the current monitoring signals ISEN_1, ISEN_2, ... ISEN_N and the voltage monitoring signal VSEN. The control signal DRV3 is used to adjust the second output voltage VOUT2 according to the power demand of the lighting module 926, and synchronously drive the operating frequency of the controller 924 and the operating frequency of the DC/DC controller 914. The endpoint PWM receives the dimming signal DIM from the control signal 928. The endpoint BLON receives the ON/OFF signal from the control module 928. The drive controller 924 controls the signal according to the ON/OFF signal and the dimming signal DIM from the control module 928 to activate or deactivate the illumination module 926, and also generates the dimming signal DIM to adjust the brightness of the illumination module 926.

FIG. 10 is a circuit diagram of a drive controller 924 suitable for FIG. 9 in accordance with an embodiment of the present invention. In the embodiment shown in FIG. 10, the drive controller 924 includes a current adjustment unit 1004, a reference signal generator 1010, an error amplifier 1008, a ramp signal generator 1012, a comparator 1006, an inverting buffer 1002, an overvoltage protection, and Voltage regulation circuit 1014 and switch 1020, wherein switch 1020 is controlled by overvoltage protection and voltage regulation circuit 1014. Figure 10 will be described in conjunction with Figure 9.

In one embodiment, current adjustment unit 1004 equalizes the current flowing through the plurality of sets of LED strings in illumination module 926 such that the current flowing through each of the LED strings is substantially equal to the target current value. Here, "substantially equal" means that the current flowing through the LED string can be different, but the difference is limited to a certain range. Each LED string is caused to produce a light output of substantially the same brightness as desired.

In addition, the current adjustment unit 1004 adjusts the second output voltage VOUT2 to meet the power demand of the lighting module 926. In particular, in one embodiment, current adjustment unit 1004 adjusts second output voltage VOUT2 such that the voltage drop across each set of LED strings is sufficient to cause each set of LED strings to produce a current that is approximately equal to the target current value. The current adjustment unit 1004 receives the monitoring signals ISEN_1, ISEN_2, . . . ISEN_N indicating the LED string currents flowing through the illumination module 926, respectively. The current adjustment unit 1004 controls the reference signal generator 1010 to control the activation or deactivation of the illumination module 926 and the brightness according to the ON/OFF signal and the dimming signal DIM, respectively.

The reference signal generator 1010 generates a reference signal ADJ according to the power demand of the lighting module 926. In one embodiment, the current adjustment unit 1004 controls the reference signal generator 1010 to raise or lower the reference signal ADJ to raise or lower the second output voltage VOUT2 accordingly. For example, the current adjustment unit 1004 selects a monitoring signal of a minimum value from the monitoring signals ISEN_1 to ISEN_N. When the minimum monitored signal is below the preset threshold, the current adjustment unit 1004 raises the reference signal ADJ. When the minimum monitoring signal is above the preset threshold, the current adjustment unit 1004 lowers the reference signal ADJ. Since the smallest current monitoring signal among the current monitoring signals ISEN_1~ISEN_N corresponds to the LED string having the largest forward voltage. The power supply requirements of all of the LED strings in the lighting module 926 can be met based on the minimum current monitoring signal conditioning reference signal ADJ. The error amplifier 1008 receives the reference signal ADJ and a voltage monitoring signal indicating the second output voltage VOUT2, and generates an error signal ER by comparing the reference signal ADJ and the voltage monitoring signal VSEN. In one embodiment, the error amplifier 1008 raises the error signal when the reference signal ADJ rises. ER.

The ramp signal generator 1012 receives the synchronization signal SYNC from the secondary coil L1 indicating the operating frequency of the DC/DC controller 914. The ramp signal generator 1012 generates a ramp signal RAMP based on the sync signal SYNC to synchronize the operating frequency of the drive controller 924 with the operating frequency of the DC/DC controller 914. Specifically, when the control signal DRV1 is in the first state (eg, logic 1), the switch Q1 is turned on. The current I _LP flows through the primary coil LP, no current flows through the secondary coil L1, and the voltage of the synchronization signal SYNC is at the first level. When the control signal DRV1 is in the second state (eg, logic 0), the switch Q1 is turned off, and the current I _L1 flows through the secondary coil L1, and the voltage of the synchronization signal SYNC is at the second level. Therefore, the drive controller 924 monitors the operating frequency of the DC/DC controller 914 based on the voltage level of the synchronization signal SYNC. When the voltage of the synchronization signal SYNC is at the first level, the ramp signal generator 1012 stops generating the ramp signal RAMP. When the voltage of the synchronization signal SYNC is at the second level, the ramp signal generator 1012 generates a ramp signal.

The comparator 1006 compares the error signal ER and the ramp signal RAMP and generates a signal DRV3B according to the power demand of the lighting module 926. In one embodiment, inverting buffer 1002 inverts signal DRV3B to generate control signal DRV3, and control signal DRV3 is used to control switch Q3 (eg, a PMOSFET coupled to secondary coil L2). In the embodiment shown in FIG. 10, the signal DRV3B and the control signal DRV3 are both pulse width modulated signals, such as PWM signals. When the control signal DRV3 is in the first state (eg, logic 0), the switch Q3 is turned on. When the control signal DRV3 is in the second state (eg, logic 1), the switch Q3 is turned off. The duty cycle of the control signal DRV3 is determined by the error signal ER. In one embodiment, if the error signal ER is raised, comparison The device 1006 raises the duty cycle of the control signal DRV3. Therefore, the average current flowing through the secondary coil L2 increases, and thus the second output voltage VOUT2 rises.

Further, the drive controller 924 monitors the operating frequency of the DC/DC controller 914 and generates a control signal DRV3 based on the synchronization signal SYNC. Specifically, when the voltage of the synchronization signal SYNC is at the second level, the ramp signal generator 1012 generates a ramp signal RAMP. Comparator 1006 compares error signal ER and ramp signal RAMP to produce signal DRV3B. Then, the inverting buffer 1002 outputs a control signal DRV3. When the voltage of the synchronization signal SYNC is at the first level, the ramp signal generator 1012 stops generating the ramp signal RAMP, and the voltage of the ramp signal RAMP is maintained at a preset maximum value. In the embodiment shown in FIG. 10, the comparator 1006 compares the preset maximum value of the error signal ER and the ramp signal RAMP to output a control signal DRV3B at logic 0, and the inverter buffer 1002 outputs a control signal DRV3 at logic 1. To open the switch Q3 (for example, PMOSFET). Therefore, the operating frequency of the drive controller 924 at the secondary coil end is synchronized with the operating frequency of the DC/DC controller 914 at the primary coil end to avoid the beat frequency between the DC/DC controller 914 and the drive controller 924. The resulting audio noise (Audible Noise).

In one embodiment, the drive controller 924 further includes a switch 1020 coupled between the overvoltage protection and voltage regulation circuit 1014 and ground. When the voltage VFB of the feedback signal is higher than the target regulation voltage, or when the voltage of the voltage monitoring signal VSEN is greater than the preset safety voltage, the overvoltage protection and voltage regulation circuit 1014 turns on the switch 1020 to pull the compensation signal VCOMP low to zero. Therefore, the current flowing through the optical coupler 916 (for example, the feedback signal FB) is increased to the maximum value. The DC/DC controller 914 reduces the duty cycle of the control signal DRV1. When the voltage VFB of the feedback signal is lower than the target adjustment voltage, and the voltage When the voltage of the monitor signal VSEN is lower than the preset safe voltage, the overvoltage protection and voltage regulating circuit 1014 turns off the switch 1020. Therefore, the drive controller 924 prevents the lighting module 926 and the control module 928 from overvoltage.

Figure 11 is a waveform diagram of display system 900 shown in Figure 9 in accordance with an embodiment of the present invention. Figure 11 will be described in conjunction with Figure 9. Specifically, FIG. 11 shows a control signal DRV1 generated by the DC/DC controller 914, a state of the switch Q1, a voltage of the synchronization signal SYNC, a current I _LP flowing through the primary coil LP, and a current flowing through the secondary coil L1. I _L1 , a control signal DRV2 generated by the drive controller 924, and a current I _L2 flowing through the secondary coil _L2 .

In operation, DC/DC controller 914 receives a monitor signal LPSEN indicative of current I _LP flowing through primary coil LP and generates control signal DRV1 to control switch Q1. If the control signal DRV1 is in the first state (eg, logic 1), the switch Q1 is turned on, and the current I _LP flowing through the primary coil LP is increased. When the switch Q1 is turned on, since the diode D1 connected to the secondary coil L1 and the diode D2 connected to the secondary coil L2 are both reverse-biased, no current flows through the secondary coils L1 and L2. The voltage of the sync signal SYNC is at the first level. When the voltage of the monitoring signal LPSEN increases to a preset voltage value, the current I _{LP is} increased to a preset current value IPK, and the DC/DC controller 314 causes the control signal DRV1 to be in a second state (eg, a logic 0 state). Turn on the switch Q1. The current I _LP flowing through the secondary coil L1 and the voltage of the synchronization signal SYNC are at the second level.

In one embodiment, when switch Q1 is open, current I _LP flowing through primary coil LP is reduced to zero. The current I _L1 flowing through the secondary coil _L1 and I _L2 flowing through the secondary coil _L2 are both reduced and both are regulated by the switch Q3. The conduction state of the switch Q3 is determined by the control signal DRV3. For example, when control signal DRV3 is in a first state (eg, logic 0), switch Q3 is turned "on". When the control signal DRV3 is in the second state (eg, logic 1), the switch Q3 is turned off. It is assumed that the number of turns of the primary coil LP is NP, the number of turns of the secondary coil L1 is N1, and the number of turns of the secondary coil L2 is N2. When the control signal is in a first state DRV3 (e.g., logic 0), the switch Q3 is turned on, the current I _L1 flows through diode D1 from the secondary coil L1, to flow control module 928. The current I _L2 flows from the ground through the switch Q3, the secondary coil L2, and the diode D2 to the lighting module 926. When switch Q3 is turned on, I _L1 and I _L2 can be expressed as: NP*I _LP =N1*I _L1 +N2*I _L2 (7)

If the control signal DRV2 is in the second state, the switch Q2 is turned off and I _L2 remains off. When switch Q2 is open, I _L1 can be expressed as: NP* I _LP =NI* I _L1 (8)

To illustrate the relationship of the currents I _LP , I _L1 and I _L2 , it is assumed that the current I _LP gradually decreases to zero. In one embodiment, transformer 932 operates in a fixed frequency mode with control signal DRV1 having a fixed frequency and an adjustable duty cycle. In another embodiment, the frequency and duty cycle of the control signal DRV1 are both adjustable.

In one embodiment, drive controller 924 generates control signal DRV3 based on synchronization signal SYNC. Specifically, when the voltage of the synchronization signal SYNC is at the first level, the control signal DRV3 remains in the second state (eg, logic 1) to turn off the switch Q3. When the voltage of the synchronization signal SYNC is at the second level, the control signal DRV3 including a plurality of pulses alternately turns on or off the switch Q3. Advantageously, the operating frequency of the drive controller 924 at the secondary coil end is synchronized with the operating frequency of the DC/DC controller 914 at the primary coil end, effectively avoiding the DC/DC controller 914 and the drive controller 924. The audio noise caused by the beat frequency.

As shown in FIGS. 9 and 11, the DC/DC controller 914 adjusts the first output voltage VOUT1 at the secondary coil L1 by controlling the received input power of the primary coil LP. Specifically, the DC/DC controller 914 controls the switch Q1 in series with the primary coil LP based on the feedback signal FB and the monitor signal LPSEN. The feedback signal FB indicates the target level of the first output voltage VOUT1. The monitor signal LPSEN indicates the current I _{LP of the} primary coil _LP . The drive controller 924 adjusts the second output voltage generated at the secondary coil L2 by controlling the switch Q3 in series with the secondary coil L2 and according to the current detection signals ISEN_1, ISEN_2...ISEN_N, the voltage of the voltage monitoring signal VSEN, and the synchronization signal SYNC. VOUT2. The current monitoring signals ISEN_1, ISEN_2 ... ISEN_N indicate the currents flowing through the respective LED strings in the illumination module 926, respectively. The voltage monitoring signal VSEN indicates the second output voltage VOUT2. The sync signal SYNC indicates the operating frequency of the DC/DC controller 914. Therefore, the boost converter 122 in the conventional display system 100 or the DC/DC controller 216, the transformer 232, and the optocoupler 234 in the conventional display system 200 can be omitted, thereby saving cost.

12 is a flow chart showing a method of controlling a transformer to generate a plurality of output voltages in accordance with an embodiment of the present invention. Figure 12 will be described in conjunction with Figure 9.

In step 1202, a transformer (eg, transformer 932 in FIG. 9) produces a first output voltage at the first secondary coil L1. In step 1204, the transformer is at a second output voltage at the second secondary winding L2. In step 1206, input power received at the primary winding LP of the transformer is controlled based on a control signal (eg, control signal DRV1 generated by DC/DC controller 914) to adjust the first output voltage.

In step 1208, a pulse width modulation signal is generated (e.g., using control signal DRV3 generated by drive controller 924 in FIG. 9). In one embodiment, the pulse width modulation signal is synchronized with the control signal. In step 1210, the pulse width modulation signal alternately turns on and off the current flowing through the second secondary winding L2 to adjust the second output voltage. For example, the pulse width modulation signal controls a switch (eg, switch Q3 in FIG. 9) coupled to the second secondary coil L2 to regulate the second output voltage. If the pulse width modulation signal is in the first state, the switch is turned on, and the current flows into the load through the second secondary coil L2. If the pulse width modulation signal is in the second state, the switch is turned off, and the current flowing through the second secondary coil L2 is turned off.

The above detailed description and the accompanying drawings are only typical embodiments of the invention. It is apparent that various additions, modifications and substitutions are possible without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood by those skilled in the art that the present invention may be changed in form, structure, arrangement, ratio, material, element, element, and other aspects without departing from the scope of the invention. The scope of the present invention is to be construed as being limited by the description

100‧‧‧Display system

102‧‧‧AC power supply

104‧‧‧AC/DC converter

106‧‧‧Primary coil

108‧‧‧second secondary coil

110‧‧‧First secondary coil

112‧‧‧ switch

114‧‧‧DC/DC controller

116‧‧‧Optocoupler

118‧‧‧Error amplifier

120‧‧ ‧ voltage divider

122‧‧‧Boost Converter

126‧‧‧Lighting module

128‧‧‧Control Module

130‧‧‧Transformers

200‧‧‧Display system

202‧‧‧Second switch

204‧‧‧First switch

214‧‧‧First DC/DC controller

216‧‧‧Second DC/DC controller

230‧‧‧First transformer

232‧‧‧Second transformer

234‧‧‧Second optocoupler

236‧‧‧First Optocoupler

300‧‧‧Display system

301‧‧‧DC/DC converter

302‧‧‧AC power supply

304‧‧‧Bridge rectifier

314‧‧‧DC/DC controller

316‧‧‧Optocoupler

318‧‧‧Error amplifier

320‧‧ ‧ voltage divider

324‧‧‧Drive Controller

326‧‧‧Lighting module

328‧‧‧Control Module

330‧‧‧ Current monitor

332‧‧‧Transformers

338‧‧ ‧ voltage divider

402‧‧‧Inverting buffer

404‧‧‧current adjustment unit

406‧‧‧ comparator

408‧‧‧Error amplifier

410‧‧‧Reference signal generator

412‧‧‧Ramp signal generator

600‧‧‧ display system

601‧‧‧DC/DC converter

614‧‧‧DC/DC controller

632‧‧‧Transformer

800‧‧‧ Method flow chart

802, 804, 806, 808, 810 ‧ ‧ steps

900‧‧‧Display system

901‧‧‧DC/DC converter

902‧‧‧AC power supply

904‧‧‧Bridge rectifier

914‧‧‧DC/DC controller

916‧‧‧Optocoupler

920‧‧ ‧ voltage divider

924‧‧‧Drive Controller

926‧‧‧Lighting module

928‧‧‧Control Module

932‧‧‧Transformer

938‧‧ ‧ voltage divider

1002‧‧‧Inverting buffer

1004‧‧‧ Current adjustment unit

1006‧‧‧ comparator

1008‧‧‧Error amplifier

1010‧‧‧Reference signal generator

1012‧‧‧Ramp signal generator

1014‧‧‧Overvoltage protection and voltage regulation circuit

1020‧‧‧ switch

1202, 1204, 1206, 1208, 1210‧ ‧ steps

The technical method of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments to make the features and advantages of the present invention more obvious. Among them: Figure 1 shows a schematic diagram of a traditional display system.

Figure 2 shows a schematic diagram of another conventional display system.

3 is a circuit diagram of a display system in accordance with an embodiment of the present invention.

4 is a circuit diagram of the driver controller shown in FIG.

FIG. 5 is a signal waveform diagram of the display system shown in FIG.

6 is a circuit diagram of a display system in accordance with another embodiment of the present invention.

Fig. 7 is a signal waveform diagram of the display system shown in Fig. 6.

8 is a flow chart showing a method of controlling a transformer to generate a plurality of output voltages in accordance with an embodiment of the present invention.

FIG. 9 is a circuit diagram of a display system according to still another embodiment of the present invention.

Figure 10 is a circuit diagram of a drive controller suitable for use in Figure 9 in accordance with an embodiment of the present invention.

Figure 11 is a waveform diagram of the display system shown in Figure 9 in accordance with an embodiment of the present invention.

12 is a flow chart showing a method of controlling a transformer to generate a plurality of output voltages in accordance with an embodiment of the present invention.

900‧‧‧Display system

901‧‧‧DC/DC converter

902‧‧‧AC power supply

904‧‧‧Bridge rectifier

914‧‧‧DC/DC controller

916‧‧‧Optocoupler

920‧‧ ‧ voltage divider

924‧‧‧Drive Controller

926‧‧‧Lighting module

928‧‧‧Control Module

932‧‧‧Transformer

938‧‧ ‧ voltage divider

Claims (24)

A DC/DC converter includes: a transformer including a primary coil, a first secondary coil, and a second secondary coil, the primary coil coupled to a power source, the first secondary coil being directed to a first load Providing a first output voltage, the second secondary coil providing a second output voltage to a second load; a switch controller coupled to the primary coil, controlling a first switch coupled to the primary coil to Controlling an input power received by the primary coil, and adjusting the first output voltage according to a power demand of the first load; and a driving controller coupled to the second secondary coil to generate a pulse width modulation signal Alternatingly turning on and off a second switch coupled to the second secondary coil, and adjusting the second output voltage according to a power demand of the second load, wherein the driving controller receives the first switch a synchronization signal of the secondary coil indicating an operating frequency of the switch controller, and generating the pulse width modulation signal according to the synchronization signal to synchronize an operating frequency of the driving controller with the opening Turn off the operating frequency of the controller. The DC/DC converter of claim 1, further comprising: an auxiliary coil for supplying a supply voltage to the switch controller. A DC/DC converter according to claim 1, wherein a source of the second switch receives the first output voltage from the first secondary winding. For example, the DC/DC converter of Patent Application No. 1 is further The method includes a transient voltage suppressor coupled between a source and a drain of the second switch. The DC/DC converter of claim 1, wherein the switch controller generates a pulse width modulation signal, alternately turns on and off the first switch, and transmits one of the pulse width modulation signals. The duty cycle adjusts the first output voltage. The DC/DC converter of claim 1, further comprising: a reference signal generator for generating a reference signal according to the power demand of the second load; and an error amplifier for receiving the reference signal and indicating the first And a monitoring signal of the output voltage, and generating an error signal by comparing the reference signal with the monitoring signal. The DC/DC converter of claim 6, wherein the second load comprises a plurality of light sources. The DC/DC converter of claim 7, wherein the drive controller includes a current adjustment unit that equalizes a plurality of currents flowing through the plurality of light sources. The DC/DC converter of claim 6, wherein the drive controller comprises: a comparator that compares the error signal with a ramp signal to generate the pulse width modulation signal. The DC/DC converter of claim 1, wherein the pulse width modulation signal is when the synchronization signal is at a first level. Keeping constant, the second switch is turned off; when the sync signal is at a second level, the pulse width modulated signal includes a plurality of pulses to alternately turn the second switch on and off. A DC/DC converter according to claim 1, wherein the drive controller reduces the input power received by the primary coil when a feedback signal indicating the first output voltage is greater than a target adjustment voltage. The DC/DC converter of claim 1, wherein when a voltage indicating a monitoring signal of the second output voltage is greater than a predetermined safety voltage, the driving controller reduces the received by the primary coil Input power. A drive controller for controlling a first output voltage output from a transformer to a load, comprising: a synchronization terminal receiving a synchronization signal from a first secondary winding of the transformer, indicating a switch controller An operating frequency; a voltage monitoring terminal receiving a voltage monitoring signal indicative of the first output voltage; at least one current monitoring endpoint receiving a current monitoring signal indicative of at least one current flowing through the load; and a drive end And generating a pulse width modulation signal according to the synchronization signal, the voltage monitoring signal, and the current monitoring signal to adjust the first output voltage, and an operating frequency of the driving controller and the operating frequency of the switch controller Synchronization, wherein the drive controller is coupled to a second secondary coil of the transformer. Such as the drive controller of claim 13 of the patent scope, wherein the pulse The rush width modulation signal alternately turns on and off a first switch coupled to a primary coil of the transformer, and controls an input power received by the primary coil to pass a responsibility of adjusting the pulse width modulation signal The cycle adjusts a second output voltage. The drive controller of claim 14, wherein the drive controller reduces a power of the second secondary coil when a feedback signal indicating the second output voltage is greater than a target adjustment voltage. The driving controller of claim 13, wherein the pulse width modulation signal alternately turns on and off a second switch coupled to the second secondary coil, and adjusts the power according to a power demand of the load. The first output voltage. The drive controller of claim 16, wherein a source of the second switch receives the second output voltage from the first secondary coil. The drive controller of claim 13, wherein when the pulse width modulation signal is in a first state, a current flows through the second secondary coil. The drive controller of claim 18, wherein when the pulse width modulation signal is in a second state, the current flowing through the second secondary coil is cut off. The drive controller of claim 18 or 19, wherein the pulse width modulation signal is maintained in the second state when the synchronization signal is at a first level, wherein the synchronization signal is in a second state At the time of the timing, the pulse width modulation signal includes a plurality of pulses. Such as the drive controller of claim 13 of the patent scope, wherein the negative The load includes a plurality of light sources. The drive controller of claim 21, wherein the drive controller further comprises a current adjustment unit that receives the plurality of current monitoring signals of the plurality of light sources and according to an ON/OFF signal and a The dimming signal controls the on/off state and brightness of the plurality of light sources, respectively. The drive controller of claim 13, wherein the drive controller reduces a power of the second secondary coil when a voltage of the voltage monitoring signal is greater than a predetermined safety voltage. The driving controller of claim 13 further includes: a third switch coupled between an overvoltage protection circuit and ground, the overvoltage protection circuit turning on the third switch to lower a compensation signal To zero.