Patent ID: 8730228

Claim:
A driving circuit comprising: a pulse modulator configured to generate a first pulse signal the duty ratio of which is adjusted such that a detection voltage which indicates the electrical state of a light emitting diode to be driven matches a predetermined reference voltage; a pulse transformer including a primary coil and a secondary coil, and arranged such that the first pulse signal is applied to the primary coil; a switching regulator including a switching element, wherein an ON/OFF operation of which is controlled according to a signal that originates at the secondary coil of the pulse transformer, and configured to stabilize an input voltage, and to output the input voltage thus stabilized to a first terminal of the light emitting diode; and a constant current circuit connected to a second terminal of the light emitting diode, wherein the pulse modulator adjusts the duty ratio of the first pulse signal such that the electric potential at the second terminal matches the predetermined voltage, and wherein the light emitting diode is a backlight of a liquid crystal display, and wherein the driving circuit further comprises: a PLL circuit configured to receive a vertical synchronization signal which is synchronized with the image data to be displayed on the liquid crystal display, and to multiply the vertical synchronization signal so as to generate a clock signal; and a duty ratio setting unit configured to count the clock signal so as to generate a pulse-modulated pulse modulation signal, and wherein the constant current circuit switches on and off a driving current that flows through the light emitting diode, according to the pulse modulation signal.