TWI606748B - Driving system, driving circuit, and scanning circuit of light emitting diodes - Google Patents

Description

Driving system, driving circuit and scanning circuit of light emitting diode

The invention relates to a driving system, a driving circuit and a scanning circuit of a light emitting diode, in particular to a driving system, a driving circuit and a scanning circuit capable of accurately driving a light emitting diode.

Please refer to FIG. 1A , which is a schematic diagram of a conventional driving system for a light emitting diode. As shown in FIG. 1A, the drive system 10 is electrically coupled to a display panel 20. The display panel 20 is provided with four drive lines DRV1 to DRV4 and four scan lines SRH1 to SRH4. The drive lines DRV1 to DRV4 are sequentially arranged to cross the scan lines SRH1 to SRH4. Each of the driving lines DRV1 to DRV4 and each of the scanning lines SRH1 to SRH4 are electrically connected to a light emitting diode, respectively, and are respectively LEDs D11, D12, D13, D14, D21, D22, D23, D24, D31, D32, D33, D34, D41, D42, D43 and D44.

The drive system 10 is mainly composed of a drive circuit 12 and a scan circuit 14. As shown in FIG. 1A, the scanning circuit 14 periodically scans four scanning lines SRH1 to SRH4 in sequence. At this time, the scanned scan line will be grounded so that the voltage on the scanned scan line drops to the ground voltage. The voltage on the scan line that has not been scanned will be an unknown voltage value. The driving circuit 12 is configured to supply driving power (which may be voltage or current) to the LEDs D11 to D44 disposed on the driving lines DRV1 to DRV4, thereby controlling the LEDs D11 to D44 to emit light and thereby Displayed on the display panel 20. In this case, a light-emitting diode that does not emit light is defined as a light-emitting diode D11, for example, a light-emitting diode of the light-emitting diode D21, and a light-emitting diode that emits light for a short time, for example, a light-emitting diode. The aspect of the polar body D22.

For example, the drive system 10 sets only the light-emitting diode D21 to emit light. Therefore, when the scanning circuit 14 scans the scanning line SRH1 (that is, the voltage on the scanning line SRH1 is the ground voltage), the driving circuit 12 outputs driving power to the driving line DRV2 so that the voltages of the anode and the cathode of the light-emitting diode D21 are made. The difference is greater than or equal to the cut-in voltage of the light-emitting diode D21. At this time, the light-emitting diode D21 is turned on, and the light-emitting diode D21 emits light and is displayed on the display panel 20.

However, as shown in FIG. 1A, since the anodes of the light-emitting diodes D21 to D24 are on the same driving line DRV2, the anode voltages of the light-emitting diodes D21 to D24 are the same. As is apparent from the above example, since the scanning circuit 14 periodically scans the four scanning lines SRH1 to SRH4 in sequence, the scanning circuit 14 sequentially scans the scanning lines SRH2 to SRH4 after scanning the scanning line SRH1. If the voltage difference between the voltage on the driving line DRV2 and the voltage on the scanning lines SRH2 to SRH4 is greater than or equal to the cutting-in voltage of the LEDs D22 to D24, the LEDs D22 to D24 (ie, the same driving line DRV2) The other light-emitting diodes will be briefly turned on for a short time, causing the drive system 10 to not accurately control the illumination of the LEDs D11-D44.

In addition, as shown in FIG. 1B, under the same architecture, the drive system 10 sets the light-emitting diodes D11, D22, D33, and D44 to emit light. While the scanning circuit 14 is switching from the scanning line SRH1 to the scanning line SRH2, the driving circuit 12 has stopped supplying the driving power to the driving line DRV1. At this time, the voltage on the driving line DRV1 is still maintained at a cut-in voltage close to the light-emitting diode. Next, the scanning circuit 14 scans to the scanning line SRH2 so that the voltage on the scanning line SRH2 drops to the ground voltage. At this time, the voltage difference between the anode and the cathode of the light-emitting diode D12 is close to the cut-in voltage of the light-emitting diode D12, causing the light-emitting diode D12 to be turned on briefly. The light-emitting diode D12 is caused to emit light for a short time. The other LEDs D23, D34, and D41 are also briefly turned on for a short time when the scanning circuit 14 sequentially scans the scanning lines SRH3, SRH4, and SRH1, causing the driving system 10 to accurately control the illumination. The polar body D11~D44 emits light.

Therefore, if the drive system 10 can accurately control the light emission of the light-emitting diodes D11 to D44, the display quality of the display panel 20 can be improved.

The technical problem to be solved by the present invention is to provide a driving system, a driving circuit and a scanning circuit for a light emitting diode to accurately control the light emitting diode illumination. The display panel has better display quality.

In one embodiment of the invention, the driving system of the light emitting diode is electrically connected to a display panel. A plurality of driving lines and a plurality of scanning lines are disposed on the display panel. A plurality of driving lines are sequentially arranged to cross the plurality of scanning lines. A light emitting diode is electrically connected between each of the driving lines and each of the scanning lines. The driving system of the light emitting diode includes a scanning circuit and a driving circuit. The scanning circuit has a plurality of scanning ends. The plurality of scanning ends are electrically connected to the plurality of scanning lines in sequence. And the scanning circuit periodically scans the plurality of scan lines sequentially. And the driving circuit has a plurality of driving ends. The plurality of driving terminals are electrically connected to the plurality of driving lines in sequence. The driving circuit supplies a driving power to the at least one driving line during a driving to drive the corresponding light emitting diode. When the corresponding light-emitting diode is turned on, the voltage of the corresponding driving terminal rises. The driving circuit provides at least one driving line-discharging path after the driving period to reduce the voltage of the corresponding driving end.

In one embodiment of the invention, the driving circuit of the above-described light emitting diode is suitable for a driving system. The drive system is electrically connected to a display panel. A plurality of driving lines and a plurality of scanning lines are disposed on the display panel. A plurality of driving lines are sequentially arranged to cross the plurality of scanning lines. Each of the driving lines and each of the scanning lines are electrically connected to a light emitting diode, and the plurality of scanning lines are electrically connected to a scanning circuit. The driving circuit includes a plurality of driving ends, a plurality of driving switches and a plurality of step-down components. Multiple drive terminals are electrically connected in sequence For multiple drive lines. A plurality of driving switches are serially connected between a power source and a plurality of driving terminals. The at least one driving switch turns on a driving period according to a driving signal, so that the power source generates a driving power to the corresponding driving line to drive the corresponding light emitting diode. When the corresponding light-emitting diode is turned on, the voltage of the corresponding driving terminal rises. The plurality of step-down components are electrically connected to the plurality of driving terminals in sequence. After the driving period, the buck elements of the corresponding driving lines are enabled according to a step-down signal, and a corresponding driving line-discharging path is provided to reduce the voltage of the corresponding driving end.

In one embodiment of the invention, the scanning circuit of the above-described light emitting diode is suitable for a driving system. The drive system is electrically connected to a display panel. A plurality of driving lines and a plurality of scanning lines are disposed on the display panel. A plurality of driving lines are sequentially arranged to cross the plurality of scanning lines. A light emitting diode is electrically connected between each of the driving lines and each of the scanning lines. The plurality of driving lines are electrically connected to a plurality of driving ends of a driving circuit in sequence. The scanning circuit includes a plurality of scanning ends, a plurality of scanning switches and a plurality of boosting elements. The plurality of scanning ends are electrically connected to the plurality of scanning lines in sequence. The plurality of scan switches are electrically connected between the plurality of scan ends and a ground end. The plurality of scan switches periodically turn on a scan period according to a scan signal. The plurality of boosting elements are sequentially electrically connected to the plurality of scanning ends, and according to the closing of the plurality of scanning switches, a plurality of scanning lines corresponding to the plurality of scanning switches are provided to increase the voltage of the corresponding plurality of scanning ends. .

In summary, the driving system, the driving circuit and the scanning circuit of the LED are provided for driving a plurality of LEDs on the display panel. The display panel is provided with a plurality of driving lines and a plurality of scanning lines, and each of the light emitting diodes is respectively disposed between the intersection of the corresponding driving line and the corresponding scanning line. A buck element is disposed on each drive line and/or a boost element is disposed on each scan line. When the driving system drives at least one target light-emitting diode in the light-emitting diode, the driving system activates the corresponding step-down element and the corresponding step-up element to avoid turning on other light-emitting diodes other than the target light-emitting diode. Accordingly, the driving system, the driving circuit and the scanning circuit of the present invention can accurately control the light emission of the light emitting diode.

In order to further understand the features and technical contents of the present invention, please refer to the following The detailed description of the present invention and the accompanying drawings are intended to illustrate the invention and not to limit the scope of the invention.

10, 100, 300‧‧‧ drive system

12‧‧‧Drive circuit

14‧‧‧Scan circuit

50, 55‧‧‧ control circuit

120, 320‧‧‧ drive circuit

130, 330‧‧‧ Scanning circuit

111, 112, 113, 114, 311, 312, 313, 314‧‧‧ drive switch

121, 122, 123, 124‧‧‧ buck components

131, 132, 133, 134, 331, 332, 333, 334‧‧ scan switches

141, 142, 143, 144, 341, 342, 343, 344‧‧‧ boost components

20,200‧‧‧ display panel

BC1, BC2, BC3, BC4‧‧‧ buck signal

BST1, BST2, BST3, BST4‧‧‧ boost signal

D11, D12, D13, D14, D1n, D21, D22, D23, D24, D2n, D31, D32, D33, D34, D3n, D41, D42, D43, D44, Dm1, Dm2, Dm3, Dmn‧‧ Polar body

DM‧‧‧ diode module

DRV1, DRV2, DRV3, DRV4, DRVm‧‧‧ drive lines

EC1, EC2, EC3, EC4‧‧‧ drive signals

GND‧‧‧ ground terminal

PW1, PW2, PW3, PW4‧‧‧ power supply

SRH1, SRH2, SRH3, SRH4, SRHn‧‧‧ scan lines

SC1, SC2, SC3, SC4‧‧‧ scan signals

SWH‧‧‧Boost Switch

SWL‧‧‧Buck Switch

R‧‧‧resistance

RS‧‧‧ short circuit resistance

T1, T2, T3, T4‧‧‧ scan period

TL1, TL2, TL4‧‧‧ buck period

TP1, TP2, TP4‧‧‧ drive period

VCHG‧‧‧ boost voltage

VDIS‧‧‧ step-down voltage

VIN‧‧‧Rising power

VO1, VO2, VO3, VO4, VOm‧‧‧ drive

VS1, VS2, VS3, VS4, VSn‧‧‧ scan end

Z‧‧‧Zina diode

FIG. 1A is a schematic diagram of a conventional driving system of a light emitting diode.

FIG. 1B is a schematic diagram of another conventional driving system of a light-emitting diode.

2A is a schematic diagram of a driving system of a light emitting diode according to an embodiment of the present invention.

2B is a circuit diagram of a driving system of a light emitting diode according to an embodiment of the present invention.

2C is a timing diagram of a driving system driving a light emitting diode according to an embodiment of the present invention.

2D is a schematic diagram of a step-down element according to an embodiment of the present invention.

3A is a schematic diagram of a boosting element in accordance with an embodiment of the present invention.

Figure 3B is a schematic illustration of a boosting element in accordance with another embodiment of the present invention.

Figure 3C is a schematic illustration of a boosting element in accordance with another embodiment of the present invention.

4 is a schematic view of a short circuit of a light-emitting diode according to an embodiment of the present invention.

FIG. 5A is a schematic diagram of a driving system of a light emitting diode according to another embodiment of the present invention.

FIG. 5B is a timing diagram of a driving system driving a light emitting diode according to an embodiment of the present invention.

In the following, the invention will be described in detail by way of illustration of various exemplary embodiments of the invention. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the illustrative embodiments set forth herein. In addition, the same reference numerals may be used in the drawings to represent similar elements.

First, please refer to FIG. 2A, which is a light emitting diode according to an embodiment of the invention. Schematic diagram of the drive system. The driving system 100 of the light emitting diode is electrically connected to a display panel 200 to control the light emitting diodes D11, D12, D13, ..., D1n, D21, D22, D23, ..., D2n, D31, D32, D33, ..., D3n on the display panel 200 and Dm1, Dm2, Dm3...Dmn emit light. The display panel 200 is provided with a plurality of driving lines DRV1 to DRVm and a plurality of scanning lines SRH1-SRHn. The drive lines DRV1 to DRVm are sequentially arranged in parallel and arranged perpendicularly to the scan lines SRH1-SRHn. A light-emitting diode is electrically connected to each of the driving lines DRV1 DRDRVm and one of the scanning lines SRH1-SRHn to form a plurality of display panels of the LEDs D11 D Dmn.

The driving system 100 includes a driving circuit 120 and a scanning circuit 130. The driving circuit 120 has a plurality of driving terminals VO1 to VOm, and the driving terminals VO1 to VOm are sequentially electrically connected to each of the driving lines DRV1 to DRVm. The scanning circuit 130 has a plurality of scanning ends VS1 to VSn, and the scanning terminals VS1 to VSn are sequentially electrically connected to each of the scanning lines SRH1 to SRHn.

For convenience of explanation, four display lines DRV1 to DRV4 (i.e., m = 4) and four scanning lines SRH1 to SRH4 (i.e., n = 4) are provided on the display panel 200 as follows. Please refer to FIG. 2B, which shows a circuit diagram of a driving system of a light-emitting diode according to an embodiment of the present invention. As shown in FIG. 2B, the drive lines DRV1 to DRV4 are sequentially arranged in parallel and vertically intersect with the scan lines SRH1 to SRH4. Each of the driving lines DRV1 DRDRV4 and one of each of the scanning lines SRH1 to SRH4 are electrically connected to a light emitting diode to form 16 light emitting diodes D11, D12, D13, D14, D21, D22, D23, D24. Display panels for D31, D32, D33, D34, D41, D42, D43 and D44.

The driving system 100 includes a driving circuit 120 and a scanning circuit 130. The driving circuit 120 has a plurality of driving terminals VO1 to VO4, and the driving terminals VO1 to VO4 are sequentially electrically connected to each of the driving lines DRV1 to DRV4. The scanning circuit 130 has a plurality of scanning ends VS1 to VS4, and the scanning terminals VS1 to VS4 are sequentially electrically connected to each of the scanning lines SRH1 to SRH4. Scanning circuit 130 periodically scans each scan line sequentially SRH1~SRH4. The driving circuit 120 provides a driving power to the at least one driving line during a driving to drive the corresponding light emitting diode. When the corresponding light-emitting diode is turned on, the voltages of the corresponding driving terminals VO1 to VO4 rise. And the driving circuit 120 provides the at least one driving line and the discharging path after the driving period to reduce the voltage of the corresponding driving end.

For example, during the above driving period (such as the driving period TP1 of the driving line DRV1 in FIG. 2C), the driving circuit 120 drives the corresponding driving light-emitting diodes, and the voltage on the driving terminal VO1 rises. Next, the drive circuit 120 will provide a drive line DRV1-discharge path after the drive period to thereby lower the voltage on the drive terminal VO1. The circuit relationship and implementation between the driver circuit 120 and a scan circuit 130 will be further described below.

The drive circuit 120 has a plurality of drive switches 111, 112, 113 and 114 and a plurality of buck elements 121, 122, 123 and 124. The scanning circuit 130 has a plurality of scan switches 131, 132, 133 and 134. The driving switches 111~114 are sequentially connected in series between the power sources PW1~PW4 and the driving lines DRV1~DRV4 (ie, each driving switch 111~114 receives the driving power generated by the power sources PW1~PW4, respectively), and are respectively controlled by driving. Signal EC1~EC4. The scan switches 131-134 are serially connected between the scan lines SRH1 to SRH4 and the ground GND, and are respectively controlled by the scan signals SC1 to SC4. The step-down elements 121-124 are electrically connected to the driving terminals VO1, VO2, VO3, and VO4 in sequence, and are respectively controlled by a plurality of step-down signals. In the present embodiment, the power source PW1 - PW4 can be a current source, a voltage source, or other power-feeding device that can generate driving power, which is not limited in the present invention. In addition, the driving signals EC1 to EC4, the scanning signals SC1 to SC4 and the plurality of step-down signals of the present embodiment are generated by the external control circuit 50. However, the driving signals EC1 to EC4 and the plurality of step-down signals can also be generated by the driving circuit 120, and the scanning signals SC1 to SC4 can also be generated by the scanning circuit 130, which is not limited in the present invention.

For convenience of explanation, the following external control circuit 50 generates drive signals EC1 to EC4, scan signals SC1 to SC4, and a plurality of step-down signals for explanation. therefore, When the control circuit 50 generates the drive signals EC2 and EC4 to turn on the drive switches 112 and 114, the drive lines DVR2 and DVR4 electrically connected by the turned-on drive switches 112 and 114 will receive the drive power generated by the power sources PW2 and PW4, respectively. When the control circuit 50 generates the scan signals SC1 to SC4 to sequentially turn on the scan switches 131 to 134, the scan lines SRH1 to SRH4 electrically connected to the turned-on scan switches 131 to 134 are sequentially connected to the ground through the ground GND. When the control circuit 50 generates the buck signal to enable the buck elements 121 and 123, the enable buck elements 121 and 123 provide the drive lines DRV1 and DRV3 discharge paths, so that the voltages of the drive terminals VO1 and VO3 will be lowered.

Furthermore, as shown in FIG. 2C, the control circuit 50 periodically generates the scan signals SC1, SC2, SC3, and SC4 to the corresponding scan switches 131-134 to periodically turn on the scan signals SC1 to SC4. The scan switches 131-134 are scanned for a period T1~T4. At this time, the corresponding scan lines SRH1~SRH4 will be grounded through the ground GND, so that the corresponding scan ends VS1~VS4 fall to the ground voltage (such as 0V). For example, when the control circuit 50 generates the high voltage scan signal SC2 for a scan period T2, the scan switch 132 will turn on a scan period T2 according to the scan signal SC2. At this time, the scan line SRH2 will be grounded through the ground GND, so that the scan end VS2 drops to 0V.

When the control circuit 50 drives at least one target light-emitting diode of the light-emitting diodes D11-D44, the control circuit 50 will be turned on during the scanning of the corresponding scan switch (such as the scan switch 131) (such as the scanning period T1). Corresponding driving signal (such as high voltage driving signal EC1) is generated to turn on the corresponding driving switch (such as driving switch 111) to drive the power source (such as power supply PW1) during a driving period (such as driving period TP1). The power is transmitted to the corresponding driving line (such as the driving line DRV1), and the target light emitting diode (such as the light emitting diode D1) is driven accordingly, and the voltage on the corresponding driving end (such as the driving end VO1) is raised. . In the present embodiment, the length of time during the driving period (such as the driving period TP1) is less than the length of time during the scanning period, that is, the driving signal 50 generates a driving signal during the scanning period during the driving period (such as during driving). TP1) to ensure the accuracy of the on-drive switch. Of course, the length of time during the driving period (such as the driving period TP1) may also be equal to the length of time during the scanning period, which is not limited by the present invention.

For example, as shown in FIG. 2B, if the target light-emitting diodes are the light-emitting diodes D11, D22, and D42, the control circuit 50 will turn on the scan switch 131 (ie, the control circuit 50 generates the high-voltage scan signal SC1). During the scanning period T1, the driving switch 111 is turned on (ie, the driving circuit 50 generates a high voltage driving signal EC1) for a driving period TP1, and the control circuit 50 is turned on by the scanning switch 132 (ie, the control circuit 50 generates a high voltage scanning signal SC2). During the scanning period T2, the driving switch 112 is turned on (that is, the driving signal EC2 of the high voltage is generated by the control circuit 50). The driving period TP2 and the driving driving switch 114 (that is, the driving signal EC4 for generating the high voltage by the control circuit 50) are driven for a period TP4, so that the power source The driving power generated by PW1, PW2, and PW4 is transmitted to the driving lines DRV1, DRV2, and DRV4, respectively, to drive the light-emitting diodes D11, D22, and D42 accordingly. In the present embodiment, the illuminating light-emitting diode is defined as, for example, the aspect of the light-emitting diode D11, and the non-illuminating light-emitting diode is defined as, for example, the light-emitting diode D12.

As shown in FIG. 2C, in the scanning period T1, the scanning line SRH1 is grounded through the ground GND, and during the driving period TP1, the voltage of the driving terminal VO1 will gradually rise due to the driving power. Light is emitted when the voltage difference between the both ends of the light-emitting diode D11 is higher than the cut-in voltage of the light-emitting diode D11. In the scanning period T2, the scanning line SRH2 is grounded through the ground GND, and the voltage of the driving terminal VO2 will gradually rise during the driving period TP2 and the voltage of the driving terminal VO4 will gradually increase during the driving period TP4. The light-emitting diode D22 emits light when the voltage of the driving terminal VO2 is higher than the cut-in voltage of the light-emitting diode D22, and the light-emitting diode D42 emits light when the voltage of the driving terminal VO4 is higher than the cut-in voltage of the light-emitting diode D42.

It is worth noting that the drive period of the drive switch (such as the drive period TP1 of the drive switch 111) ends and the drive period of the next drive switch (such as the drive switch) The driving period TP2) of 112 is defined as a non-driving period (not shown in the figure), and the control circuit 50 enables the corresponding step-down according to the step-down signal (such as the step-down signal BC1) during the non-driving period. The component (such as the enable buck component 121) is stepped down (such as the step-down period TL1), so that the corresponding driver terminal (such as the driver terminal VO1) receives the step-down voltage, thereby reducing the corresponding driver terminal (such as the driver). The voltage at terminal VO1). In this embodiment, the time length of the step-down period (such as the step-down period TL1) is less than the length of the non-driving period, that is, the control circuit 50 generates a high-voltage step-down signal during the non-driving period (such as a step-down signal). BC1) A step-down period (such as TL1 during buck) to ensure the accuracy of the enable buck element. Of course, the length of time during the step-down period (such as the step-down period TL1) can also be equal to the length of time during the non-driving period, which is not limited by the present invention.

Furthermore, the driving period of the corresponding driving switch (such as the driving period TP1 of the driving switch 111) and the scanning period of the next scanning switch (such as the scanning period T2 of the scanning switch 132) may be defined as a non- Drive period (not shown in the drawing). The control circuit 50 will perform a step-down period (such as the step-down period TL1) according to the step-down signal corresponding to the step-down signal (such as the step-down period TL1) during the non-driving period, so that the corresponding driver terminal (such as the step-down period TL1) The driving terminal VO1) receives the step-down voltage to thereby reduce the voltage of the corresponding driving terminal (such as the driving terminal VO1). Similarly, in the present embodiment, the time length of the step-down period (such as the step-down period TL1) is less than the length of the non-driving period, that is, the control circuit 50 generates a high-voltage step-down signal during the non-driving period ( For example, the buck signal BC1) is a buck period (such as TL1 during buck) to ensure the accuracy of the buck element. Of course, the length of time during the step-down period (such as the step-down period TL1) can also be equal to the length of time during the non-driving period, which is not limited by the present invention.

Since the voltage on the driving terminal (such as the driving terminal VO1) is reduced to be smaller than the cutting voltage of the light emitting diode (such as the light emitting diode D11), during the scanning of the subsequent scanning switch (such as the scanning switches 132 to 134) (such as T2~T4 during scanning), other LEDs on the same driving line (such as driving line DRV1) (such as LED D12, D13, D14) will not be illuminated by brief conduction. Here, the step-down voltage is preferably smaller than the cut-in voltage of the light-emitting diode to ensure that the voltage on the driving end is reduced to be smaller than the cut-in voltage of the light-emitting diode.

The structure of the step-down elements 121-124 in the drive circuit 120 will be further described below. In the present embodiment, the steps of the step-down elements 121-124 are the same, and therefore only the step-down element 121 will be described. As shown in FIG. 2D, the buck element 121 includes a buck switch SWL. One end of the step-down switch SWL is electrically connected to the corresponding driving terminal VO1. The other end of the buck switch SWL receives the buck voltage VDIS. Therefore, when the control circuit 50 generates the buck signal BC1 to turn on the buck switch SWL in the buck element 121, the drive terminal VO1 will receive the buck voltage VDIS, so that the voltage on the drive terminal VO1 drops to the buck voltage. VDIS. Similarly, the buck devices 122-124 will also be controlled by the buck signals BC2~BC4 as shown in FIG. 2C, respectively, so that the voltages of the driving terminals VO2~VO4 receiving the buck voltage VDIS are lowered to the buck voltage VDIS. . Each of the buck elements 121-124 can also be implemented in other structures, which is not limited by the present invention.

Referring to FIG. 2B and FIG. 2C simultaneously, the control circuit 50 generates the driving signal EC1 during the scanning period T1 to turn on the driving switch 111 and generates the driving signals EC2 and EC4 during the scanning period T2 to turn on the driving switches 112 and 114 to drive. Light-emitting diodes D11, D22 and D42. And the non-driving period at this time is before the start of the driving period of the driving switch and before the start of the scanning period of the next scanning switch.

Next, the control circuit 50 will end the driving period TP1 of turning on the driving switch 111 (that is, the driving signal EC1 at which the control circuit 50 generates a high voltage) to the next scanning switch 132 (that is, the scanning signal SC2 at which the control circuit 50 generates a high voltage). Before the start of the scanning period T2, a high voltage step-down signal BC1 is generated, and the step-down period TL1 is turned on to turn on the step-down switch SWL in the step-down element 121, so that the voltage on the driving terminal VO1 falls to the step-down voltage VDIS.

Similarly, the control circuit 50 will also turn to the next driving period TP2 of the driving switch 112 (ie, the driving signal EC2 that the control circuit 50 generates a high voltage). Before the start of the scanning period T3 of the scan switch 133 (ie, the high-voltage scan signal SC3), a high-voltage step-down signal BC2 is generated and a step-down period TL2 is generated to turn on the step-down in the step-down element 122. The switch SWL causes the voltage on the driving terminal VO2 to drop to the step-down voltage VDIS. And the control circuit 50 also ends the driving period TP4 of the driving switch 114 (that is, the driving signal EC4 that generates the high voltage by the control circuit 50) to the next scan switch 133 (ie, the control circuit 50 generates the high voltage scanning signal SC3). Before the start of the scanning period T3, a high voltage step-down signal BC4 is generated, a step-down period TL4, to thereby turn on the step-down switch SWL in the step-down element 124, so that the voltage on the driving terminal VO4 falls to the step-down voltage VDIS.

As can be seen from the above, the control circuit 50 charges the corresponding driving terminal (such as the driving terminal VO1) during the driving of the conduction driving switch (such as the driving period TP1 of the driving switch 111), and the control circuit 50 drives the driving of the driving switch (eg, The corresponding driving terminal (such as the driving terminal VO1) is discharged before the start of the driving period TP1) of the driving switch 111 until the scanning period of the next scanning switch (such as the scanning period T2 of the scanning switch 132) is started. After the target light-emitting diode (such as the light-emitting diode D11) is illuminated, other light-emitting diodes (such as the light-emitting diodes D12, D13, and D14) on the same driving line (such as the driving line DRV1) are not driven by the light-emitting diodes (such as the light-emitting diodes D12, D13, and D14). The voltage difference between the voltage at the terminal and the voltage at the scanning terminal is greater than or equal to the cut-in voltage of the light-emitting diode and is briefly illuminated.

For the light-emitting diodes on the diagonal, the LEDs D11, D22, D33, and D44 are described. Since the light-emitting diode D11 on the diagonal line emits light, the control circuit 50 discharges the voltage of the driving terminal VO1, so that when the control circuit 50 drives the next scanning line SRH2, the light-emitting diode D12 is driven. It does not emit light because the voltage of the driving terminal VO1 is greater than or equal to the cutting-in voltage of the light-emitting diode. Similarly, after the LEDs D23, D34, and D41 are illuminated by the LEDs D22, D33, and D44, respectively, the voltages of the driving terminals VO2 to VO3 are not shorter than or equal to the cutting voltage of the LEDs. Glowing.

Accordingly, the drive system 100 is provided with one on each of the drive lines DRV1 to DRVm. Buck switch. After the driving system 100 drives at least one target light emitting diode of the LEDs D11~Dmn, the driving system 100 turns on the corresponding step-down switch to avoid turning on other light emitting diodes other than the target light emitting diode. Accordingly, the drive system 100 can accurately control the light emission of the light emitting diode.

In addition, as shown in FIG. 2B, the scanning circuit 130 may further include a plurality of boosting elements 141, 142, 143, and 144. The boosting elements 141-144 are sequentially electrically connected to the scanning ends VS1, VS2, VS3, and VS4, and according to the closing of the scan switch, a scan line corresponding to the scan switch is provided to increase the voltage of the corresponding scan end. In the present embodiment, the boosting elements 141-144 are respectively controlled by the boosting signals BST1 B BST4 (as shown in FIGS. 2C and 3A), and the boosting signals BST1 B BST4 are generated by the external control circuit 50. The boosting signals BST1 to BST4 can also be generated by the scanning circuit 130, which is not limited in the present invention. In addition, the boosting elements 141-144 can also be controlled by the scanning signals SC1~SC4 (as shown in FIGS. 2C, 3B and 3C), and the invention is not limited thereto. For convenience of explanation, the boosting signals BST1 to BST4 are generated by the external control circuit 50 for explanation.

Further, during the scanning period of turning on the corresponding scan switch (such as the scan period T1 of the turn-on scan switch 131), the control circuit 50 generates a low-voltage boost signal (such as the boost signal BST1) to disable the corresponding a boosting component (such as boosting component 141) and generating a high voltage boosting signal (such as boosting signals BST2~BST4) to enable other risers other than boosting components (such as boosting component 141) The pressing elements (such as the boosting elements 142-144) are such that each of the scanning ends (such as the scanning ends VS2 to VS4) other than the corresponding scanning end (such as the scanning end VS1) receives the boosting voltage. At this time, the voltage on each scanning end (such as the scanning end VS2~VS4) other than the corresponding scanning end (such as the scanning end VS1) is raised to avoid the need to emit light on the same driving line (such as the driving line DRV1). The light-emitting diodes (such as the light-emitting diodes D12, D13, D14) emit light.

In this embodiment, the scan signals SC1~SC4 and the corresponding boost signals BST1~BST4 are reverse signals. That is, when the control circuit 50 is turned on, the corresponding driving is turned on. When turned off, other boosting elements other than the corresponding boosting elements are enabled at the same time to raise the voltage on each scanning end other than the corresponding scanning end. In addition, the difference between the step-down voltage in the step-down elements 121-124 and the boosted voltage is preferably smaller than the all-in voltage of the light-emitting diode to ensure that the light-emitting diodes that do not need to emit light on the same driving line do not emit light. .

The structure of the buck-boost elements 141-144 in the drive circuit 130 will be further described below. In the present embodiment, the boosting elements 141-144 have the same structure, and therefore only the boosting element 141 will be described.

As shown in FIG. 3A, FIG. 3A is a schematic diagram of a boosting element according to an embodiment of the present invention. In the present embodiment, the boosting element 141 includes a boost switch SWH. The one end of the boost switch 141 is electrically connected to the corresponding scan end VS1, and the other end of the boost switch 141 receives a boost voltage VCHG. Therefore, when the control circuit 50 generates the low voltage scan signal SC1 to turn off the drive switch 131, the control circuit 50 generates a high voltage boost signal BST1 to turn on the boost switch SWH in the boosting element 141 accordingly. At this time, the scan terminal VS1 on the scan line SRH1 will receive the boost voltage VCHG, so that the voltage on the scan terminal VS1 rises to the boost voltage VCHG. Similarly, boosting elements 142-144 will also be controlled by boost signals BST2~BST4 such that the voltages of scan terminals VS2~VS4 receiving boost voltage VCHG rise to boost voltage VCHG.

In another embodiment, as shown in FIG. 3B, each boosting element 141 includes a resistor R and a Zener diode Z. One end of the resistor R receives a rising power VIN. The other end of the resistor R is electrically connected to one end of the Zener diode Z. The other end of the Zener diode Z is grounded. And an end point between the resistor R and the Zener diode Z is electrically connected to the scanning end VS1. Therefore, when the control circuit 50 generates the low voltage scan signal SC1 to turn off the scan switch 131, the voltage at the end point between the resistor R and the Zener diode Z will become the boost voltage, so that the voltage on the scan terminal VS1 Rise to the boost voltage. Similarly, boosting elements 142-144 will also be controlled by scan signals SC2~SC4 such that the voltages of scan terminals VS2~VS4 rise to the boost voltage.

In addition, in another embodiment, as shown in FIG. 3C, the boosting element 141 includes a resistor R and a diode module DM connected in series with one or more diodes. One end of the resistor R receives a rising power VIN. The other end of the resistor R is electrically connected to one end of the diode module DM. The other end of the diode module DM is grounded. And an end point between the resistor R and the diode module DM is electrically connected to the scanning end VS1. Therefore, when the control circuit 50 generates the low voltage scan signal SC to turn off the scan switch 131, the voltage at the terminal between the resistor R and the diode module DM will become the boost voltage, so that the voltage on the scan terminal VS1 Rise to the boost voltage. Similarly, boosting elements 142-144 will also be controlled by scan signals SC2~SC4 such that the voltages of scan terminals VS2~VS4 rise to the boost voltage. Each of the boosting elements 141-144 can also be implemented in other configurations, which is not limited by the present invention.

In the above example, the control circuit 50 turns on the driving switch 111 during the scanning period T1 and turns on the driving switches 112 and 114 during the scanning period T2 to drive the light-emitting diodes D11, D22, and D42. For convenience of explanation, the boosting elements 141 to 144 are described by taking the boosting element shown in FIG. 3A as an example.

Referring to FIGS. 2B, 2C and 3A simultaneously, the control circuit 50 generates a boost signal BST1 of a low voltage signal and generates a high voltage during a scan period T1 of turning on the scan switch 131 (ie, the scan signal SC1 at which the control circuit 50 generates a high voltage). The boosting signals BST2 to BST4 turn off the boosting switch SWH in the boosting element 141 and turn on the boosting switch SWH in the boosting elements 142 to 144. Here, the scan signals SC1~SC4 are mutually inverted signals with the corresponding boost signals BST1~BST4. At this time, the scanning terminals VS2 VS VS4 respectively receive a boosting voltage VCHG, thereby increasing the voltage on the scanning terminals VS2 VS VS4 to the boosting voltage VCHG, thereby avoiding the light emitting diode D12 on the same driving line DRV1, D13 and D14 emit light.

Similarly, the control circuit 50 generates the boost signal BST2 of the low voltage signal and generates the high voltage boost signals BST1 and BST3 during the scan period T2 of turning on the scan switch 132 (ie, the scan signal SC2 for which the control circuit 50 generates a high voltage). And BST4, to turn off the boost switch SWH in the boosting element 142 and turn on the boosting element 141, Boost switch SWH in 143 and 144. Here, the scan signals SC1~SC4 are mutually inverted signals with the corresponding boost signals BST1~BST4. At this time, the scanning terminals VS1, VS3 and VS4 will respectively receive the boosting voltage VCHG to thereby raise the voltages on the scanning terminals VS1, VS3 and VS4 to the boosting voltage VCHG. Further, the light-emitting diodes D21, D23, and D24 on the same driving line DRV2 can be prevented from emitting light, and the light-emitting diodes D41, D43, and D44 on the same driving line DRV4 can be prevented from emitting light. Preferably, the difference between the step-down voltage in the step-down elements 121-124 and the boost-up voltage VCHG is smaller than the all-in voltage of the light-emitting diode to ensure that the light-emitting diodes that do not need to emit light on the same driving line are not Will shine.

As can be seen from the above, the control circuit 50 charges the corresponding driving terminal (such as the driving terminal VO1) during the driving period of the corresponding driving switch (such as the driving period TP1 of the driving switch 111), so that the target LED (such as the light emitting diode) Body D11) illuminates. At this time, the voltage on each scanning end (such as the scanning end 142~144) other than the corresponding scanning end (such as the scanning end 141) rises to avoid other light emitting diodes on the same driving line (such as the driving line DRV1). The voltage difference between the anode and the cathode (e.g., the light-emitting diodes D12, D13, and D14) is greater than or equal to the cut-in voltage of the light-emitting diode to emit light.

Next, please refer to FIG. 4, which shows a schematic diagram of a short circuit of the light-emitting diode according to an embodiment of the present invention. As shown in FIG. 4, the external control circuit 50 also drives the LEDs D11, D22, and D42. If the light-emitting diode D11 on the display panel 20 is short-circuited, the anode end and the cathode end of the light-emitting diode D11 will form a short-circuit resistance RS. At this time, the control circuit 50 does not form a current path in the short-circuit resistance RS of the light-emitting diode D11 during the driving of the LEDs D22 and D42.

For example, when the control circuit 50 turns on the driving switch 112 for a driving period TP2, the switching element 111 is not turned on and the step-down element 121 is not driven, so that a current path is not formed in the short-circuit resistance RS of the light-emitting diode D11. For another example, the control circuit 50 does not turn on the driving switch 111 and does not drive until the scanning period T3 of the next scanning switch 133 is turned on after the driving period TP2 of the driving switch 112 is turned on. Since the step-down element 121 is driven, the current path is not formed in the short-circuit resistance RS of the light-emitting diode D11. The process of the control circuit 50 for driving the other light-emitting diodes is substantially the same as that of the control circuit 50 for driving the light-emitting diodes D11, D22 and D42, and has been described in the above embodiments, and thus will not be described herein.

As also shown in FIG. 4, the external control circuit 50 is driving the light-emitting diode D22. If the light-emitting diode D22 on the display panel 20 is open, the voltage of the driving terminal VO2 on the driving line DRV2 rises. At this time, since the boosting elements 141, 143, and 144 raise the voltages of the scanning terminals VS1, VS3, and VS4 on the scanning lines SRH1, SRH3, and SRH4. Therefore, the light-emitting diodes D21, D23, and D24 of the same driving line DRV2 as the open-emitting LED D22 are not slightly brightened by the voltage of the driving terminal VO2.

Therefore, in the process of driving the LEDs D11, D22, and D42 to emit light, the control circuit 50 does not cause damage or light emission of other LEDs due to short-circuit or open-circuit conditions of the LEDs. Accordingly, if the light-emitting diode is short-circuited or open-circuited, the driving system 100 can accurately control the light-emitting diodes D11 to D44 to emit light.

Referring to FIG. 5A again, a schematic diagram of a driving system of a light emitting diode according to another embodiment of the present invention is shown. The driving system 300 of the present embodiment differs from the driving system 100 of the previous embodiment in that the driving circuit 320 of the driving system 300 does not have the step-down element 121 as described in the driving circuit 120 of the driving system 100. ~124, but the scanning circuit 330 of the drive system 300 has a plurality of boosting elements 341, 342, 343 and 344 controlled by an external control circuit 55. The structure and operation modes of the driving switches 311, 312, 313 and 314 in the driving circuit 320, and the scanning switches 331, 332, 333 and 334 in the scanning circuit 330, and the boosting elements 341 to 344 are substantially the same as those in FIG. 2B. The driving switches 111 to 114 of the driving circuit 120, the scanning switches 131 to 134 of the scanning circuit 130, and the boosting switches 141 to 144 have the same structure and operation mode, and therefore will not be described herein.

Therefore, as shown in FIG. 5B, the scan circuit SC1~SC4 periodically generates the scan signals SC1~SC4 to the corresponding scan switches 331-334 to The scanning switches 331 to 334 are periodically turned on in a scanning period T1 to T4. At this time, the corresponding scanning lines SRH1 to SRH4 will be grounded through the grounding terminal GND, so that the scanning ends VS1 to VS4 on the corresponding scanning lines SRH1 to SRH4 are lowered to the grounding voltage (for example, 0V).

When the target light-emitting diodes are the light-emitting diodes D11, D22, and D42, the control circuit 55 turns on the driving switch 311 for a driving period TP1 during a scanning period T1 of turning on the scanning switch 331, and turns on the scanning switch 332. During a scan period T2, the drive switch 312 is driven to drive 312 and the drive switch 314 is driven for a period TP4, so that the drive power generated by the power supplies PW1, PW2, and PW4 is transmitted to the drive lines DRV1, DRV2, and DRV4, respectively. The light-emitting diodes D11, D22 and D42 are driven.

The control circuit 55 disables the boosting element 341 and turns on the boosting element 342 other than the boosting element 341 during the scanning period T1 of turning on the scanning switch 331 (i.e., the scanning signal SC1 at which the control circuit 55 generates a high voltage). ~344, so that each of the scanning terminals VS2 to VS4 other than the scanning terminal VS1 receives the boosting voltage. At this time, the voltage on each of the scanning terminals VS2 to VS4 other than the scanning end VS1 is raised to prevent the light-emitting diodes D12, D13, and D14 on the same driving line DRV1 from emitting light. In this embodiment, the scan signals SC1~SC4 are respectively inverted signals with the corresponding boost signals BST1~BST4, that is, when the control circuit 55 turns on the scan switch 331, the other components other than the booster element 341 are simultaneously enabled. The boosting elements 342 to 344 are raised to raise the voltage on each of the scanning terminals VS2 to VS4 other than the scanning end VS1.

Similarly, the control circuit 55 disables the boosting element 342 and turns on the boosting element 342 during the scanning period T2 of turning on the scan switch 332 (ie, the scan signal SC2 at which the control circuit 55 generates a high voltage). Boost elements 341, 343 and 344. Here, the scan signals SC1~SC4 are mutually inverted signals with the corresponding boost signals BST1~BST4. At this time, the other scanning terminals VS1, VS3 and VS4 other than the scanning end VS2 will receive the boosting voltage, thereby increasing the voltages on the scanning terminals VS1, VS3 and VS4 other than the scanning end VS2. In turn, the same drive can be avoided The light-emitting diodes D21, D23, and D24 on the moving line DRV2 emit light, and the light-emitting diodes D41, D43, and D44 on the same driving line DRV4 can be prevented from emitting light.

As can be seen from the above, the control circuit 55 charges the corresponding driving terminal (such as the driving terminal VO1) during the driving of the driving switch (such as the driving period TP1 of the driving switch 311), so that the target LED (such as the LED diode D11) ) illuminate. At this time, the voltage on each scanning end (such as the scanning end 342~344) of the corresponding scanning end (such as the scanning end 341) rises to avoid other LEDs on the same driving line (such as the driving line DRV1). The voltage difference between the anode and the cathode (e.g., the light-emitting diodes D12, D13, and D14) is greater than or equal to the cut-in voltage of the light-emitting diode to emit light.

In summary, the driving system of the LEDs provided by the embodiments of the present invention has a buck element disposed on each driving line and/or a boosting element disposed on each scanning line. When the driving system drives at least one target light-emitting diode in the light-emitting diode, the driving system activates the corresponding step-down element and the corresponding step-up element to avoid turning on other light-emitting diodes other than the target light-emitting diode. Accordingly, the driving system of the present invention can accurately control the light emission of the light emitting diode.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100‧‧‧ drive system

120‧‧‧Drive circuit

130‧‧‧Scan circuit

200‧‧‧ display panel

D11, D12, D13, D1n, D21, D22, D23, D2n, D31, D32, D33, D3n, Dm1, Dm2, Dm3, Dmn‧‧‧Lighting diode

DRV1, DRV2, DRV3, DRVm‧‧‧ drive line

SRH1, SRH2, SRH3, SRHn‧‧‧ scan lines

VO1, VO2, VO3, VOm‧‧‧ drive

VS1, VS2, VS3, VSn‧‧‧ scan end

Claims (8)

A driving system of a light-emitting diode is electrically connected to a display panel, wherein the display panel is provided with a plurality of driving lines and a plurality of scanning lines, and the driving lines are sequentially disposed to intersect with the scanning lines, and each of the driving lines Each of the scan lines is electrically connected to a light-emitting diode, and the driving system of the light-emitting diode includes: a scan circuit having a plurality of scan ends, wherein the scan ends are electrically connected to the scan terminals Scanning lines, and the scanning circuit periodically scans the scan lines; and a driving circuit having a plurality of driving ends, the driving ends are sequentially electrically connected to the driving lines, and the driving circuit is in a driving period Providing a driving power to the at least one driving line to drive the corresponding light emitting diode, and when the corresponding light emitting diode is turned on, the corresponding voltage of the driving end is increased; wherein the driving circuit is after the driving period Providing the at least one driving line-discharging path to reduce a voltage of the corresponding driving end; wherein the driving circuit has a plurality of driving switches and a plurality of step-down elements, and the driving switches are sequentially arranged The step-down components are electrically connected to the driving terminals in sequence between the power source and the driving terminals, wherein the driving switches corresponding to the at least one driving line are turned on according to a driving signal, so that the power source generates the driving power to Corresponding to the driving line, and the corresponding step-down component of the driving line is enabled according to a step-down signal, so that the step-down element provides a corresponding discharge path of the driving line; wherein the scanning circuit has a plurality of scanning switches The scan switches are electrically connected between the scan ends and a ground end. The scan switches are sequentially turned on according to a scan signal, and the scan switch is turned on, and the scan is corresponding. The grounding is performed; wherein, during the scanning of the scan switch, the corresponding driving switch turns on the driving period according to the driving signal, so that the driving power generated by the power source is transmitted to the corresponding driving line, so as to drive the corresponding The light emitting diode; wherein, after the end of the driving period of the driving switch, the beginning of the scanning period of the next scanning switch is defined as a non-drive Period, and the element corresponding to the buck The non-driving period is enabled according to the step-down signal, and the corresponding driving end receives a step-down voltage to thereby reduce the voltage of the corresponding driving end, wherein the step-down period is less than or equal to the non-driving period; The scanning circuit further has a plurality of boosting components, and the boosting components are electrically connected to the scan terminals in sequence, wherein the corresponding boosting component is disabled during the scanning of the scan switch. The corresponding scanning end is grounded, and the corresponding boosting elements other than the boosting element are enabled, so that the corresponding scanning ends other than the scanning end receive a boosting voltage, and corresponding The voltages of the scan terminals other than the scan terminal are raised to the boost voltage. The driving system of the light-emitting diode of claim 1, wherein the driving period is less than or equal to the scanning period. The driving system of the LED of claim 1, wherein each of the bucking components comprises a buck switch, one end of the buck switch is electrically connected to the corresponding driving end, and the buck switch is another The buck voltage is received at one end, and when the buck switch is turned on according to the buck signal, the corresponding voltage of the driving terminal drops to the buck voltage. The driving system of the light-emitting diode of claim 1, wherein the step-down voltage is less than a cut-in voltage of the light-emitting diode. The driving system of the light-emitting diode of claim 1, wherein each of the boosting elements includes a boosting switch, one end of the boosting switch is electrically connected to the corresponding scanning end, and the boosting switch is The other end receives the boosted voltage, wherein when the boosting switch is turned on according to a boosting signal, the corresponding voltage on the scanning terminal rises to the boosting voltage. The driving system of the light-emitting diode of item 1 of the claim, wherein each of the liters The pressing element includes a resistor and a Zener diode, and one end of the resistor receives a rising power, and the other end of the resistor is electrically connected to one end of the Zener diode, and the other end of the Zener diode is grounded, and the The scanning end corresponding to an electrical connection between the resistor and the Zener diode. The driving system of the light-emitting diode of claim 1, wherein each of the boosting elements comprises a resistor and a diode module connected in series with one or more diodes, and one end of the resistor receives a rising Power, the other end of the resistor is electrically connected to one end of the diode module, the other end of the diode module is grounded, and the scan is electrically connected to an end point of the diode module. end. A driving circuit for a light-emitting diode is applicable to a driving system. The driving system is electrically connected to a display panel. The display panel is provided with a plurality of driving lines and a plurality of scanning lines, and the driving lines are sequentially scanned with the scanning lines. Each of the driving lines and each of the scanning lines are electrically connected to a light emitting diode, and the scanning lines are electrically connected to a scanning circuit, wherein the scanning circuit has a plurality of scanning ends, a plurality of scanning switches, and a plurality of boosting components, wherein the scan terminals are electrically connected to the scan lines in sequence, and the scan circuit periodically scans the scan lines sequentially, the scan switches are sequentially electrically connected to the scan ends and one Between the grounding ends, the scanning switches are periodically turned on according to a scanning signal, and when the scanning switch is turned on, the corresponding scanning end is grounded, and the boosting elements are sequentially electrically connected to the scanning. End, during the scanning of the scan switch, the corresponding boosting component is disabled, so that the corresponding scan terminal is grounded, and the corresponding boosting components other than the boosting component are enabled (ena Ble), such that the scan terminals other than the scan end receive a boost voltage, and the voltages of the scan terminals other than the scan end are raised to the boost voltage, and the driving circuit includes: a driving end, which is electrically connected to the driving lines in sequence; a plurality of driving switches are sequentially connected in series between a power source and the driving ends, to When the driving switch is turned on according to a driving signal, the driving source generates a driving power to the corresponding driving line to drive the corresponding LED, and when the corresponding LED is turned on, corresponding The voltage of the driving terminal is increased; and a plurality of step-down components are sequentially electrically connected to the driving terminals, and after the driving period, the step-down component corresponding to the driving line is enabled according to a step-down signal, and is provided Corresponding to the drive line a discharge path to reduce the voltage of the corresponding drive end; wherein, after the end of the driving period of the drive switch, the start of the scan period of the next scan switch is defined as a non-drive period, and The corresponding step-down element is enabled during the non-driving period according to the step-down signal, so that the corresponding driving end receives a step-down voltage to reduce the voltage of the corresponding driving end, wherein the step-down period is less than Equal to the non-driving period.