The constant current driving circuit can further include multichannel constant current LED controlling circuit U1 configured to control an output current of the power stage circuit to be substantially constant by controlling the state of power switching transistor Q in accordance with current feedback signal VFB that represents the output current flowing though the LED load. The value of the output current can be consistent with an expected driving current of the LED load. An average current of each LED string may be controlled in accordance with one corresponding PWM dimming signal by multichannel constant current LED controlling circuit U1, in order to achieve corresponding luminance. For example, PWM dimming signal PWM1 can control the luminance of LED string LED1, PWM dimming signal PWM2 can control the luminance of LED string LED2, and PWM dimming signal PWM3 can control the luminance of LED string LED3.

The constant current driving circuit can include a multichannel switching circuit. As shown in FIG. 5, the multichannel switching circuit can include switching transistor Q1 connected in parallel with LED string LED1, switching transistor Q2 connected in parallel with LED string LED2, and switching transistor Q3 connected in parallel with LED string LED3. Multichannel constant current LED controlling circuit U1 can connect to controlling terminals (e.g., gates) of switching transistors Q1, Q2 and Q3, to control their switching states. Switching transistors Q1, Q2 and Q3 can be controlled to periodically turn off/on corresponding LED strings in accordance with their corresponding PWM dimming signals by multichannel constant current LED controlling circuit U1.