Led driving system and closed-loop control method for led driving

A LED driving system, including:

• an LED load, whose positive terminal is connected to a bus voltage;
• a constant-current control module, connected to a negative terminal of the LED load, and configured for constant-current control of the LED load;
• an electrolytic capacitor, wherein an upper plate of the electrolytic capacitor is connected to the positive terminal of the LED load, and the electrolytic capacitor discharges to the LED load when the bus voltage is less than a voltage difference across the electrolytic capacitor;
• a discharging-voltage measuring module, connected to the negative terminal of the LED load, wherein, based on the negative terminal voltage of the LED load, the discharging-voltage measuring module determines a relative magnitude of a discharging voltage of the electrolytic capacitor and obtains a control signal;
• a bus-voltage measuring module, measuring the bus voltage to obtain a first measured voltage;
• a charging-current control module, wherein the charging-current control module is connected to the discharging-voltage measuring module, an output of the bus-voltage measuring module, and a lower plate of the electrolytic capacitor, and adjusts a charging current of the electrolytic capacitor based on the control signal and the first measured voltage;
• wherein the charging-current control module includes a compensation unit, an input of the compensation unit is connected to the discharging-voltage measuring module, and the compensation unit generates a corresponding compensation voltage based on an output signal of the discharging-voltage measuring module;
• wherein the compensation unit includes an addition and subtraction counter, which decreases the charging current of the electrolytic capacitor by performing a subtraction operation or increases the charging current of the electrolytic capacitor by performing an addition operation.