A high-side and low-side driver is widely applied to drive the switch-bridge of bridge type converters, such as active clamp forward converter, half-bridge converter and full-bridge converter. FIG. 1 shows a conventional configuration of an active clamp forward converter with a driving IC. In this converter, a low-side switch S1 (main switch) is employed in the primary side of the transformer T, and an active clamp branch is connected in parallel with the primary winding of the transformer T. The active clamp branch includes a high-side switch (active switch) S2 and a clamping capacitor C11 connected in series. The low-side switch S1 and the high-side switch S2 operating in complementary form a switch-bridge, and a high-side and low-side driving IC 1 is employed to drive the switch-bridge.
At present, the high-side driver and the low-side driver are usually integrated into one chip. The most popular design is shown in FIG. 2. In the driver IC 1 of this prior art, two input signals Hin, Lin are needed. One input signal (Lin) is a PWM signal to trigger the low-side driving circuit 3, and the other one (Hin) is the inverting signal of the PWM signal to trigger the high-side driving circuit 2. Two high voltage rated switches M1 and M2 are employed to achieve the voltage level shifting of the high-side driver 1, which is controlled by the inverting signal of the PWM signal. Several disadvantages occur due to the employment of the high voltage rated switches M1 and M2. Firstly, switching loss of these switches is significant especially at a high switching frequency. Secondly, the switches M1 and M2 are packaged into the driver IC, which increases the complicacy of the manufacturing. Thirdly, these high voltage rated switches increase the cost of the driver. Additionally, in order to drive the high-side switch S2 and the low-side switch S1 better, a dead-time setting circuit is needed to generate two complementary signals with optimized dead time. It is known that the ability of the source current and the sink current is an important factor to evaluate a driving circuit. In most of the driver ICs, the ability of the source current and sink current is limited, which will slow the turning on and turning off speed of the switch component in a larger power converter and will decrease the efficiency of the converter. Therefore, an additional buffer circuit is needed.
The present invention provides a low-cost high-side and low-side driver, which overcomes the disadvantages of the prior arts. It can be implemented by simple discrete circuits and can be integrated into one chip.