ELECTRIC POWER SUPPLY CIRCUIT AND PAM CONTROL METHOD FOR THE SAME

• US 20100073977A1
• Filed: 03/31/2008
• Published: 03/25/2010
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Industries Ltd
• Inventors: Shimatani, Keisuke, Yoshisaka, Keiichi, Hashimoto, Masafumi, Katou, Masakazu, Nakamoto, Ryou
• Granted Patent: US 8,385,095 B2
• Time in Patent Office: Days
• US Class Current: 363/126
• CPC Class Codes: H02M 1/4208 Arrangements for improving power factor of AC input
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An increase in a ripple voltage of a capacitor in a smoothing circuit is prevented to achieve a compact capacitor and cost reduction for capacitors in an electric power supply circuit which performs PAM control using a switching element.

An electric power supply circuit includes a bridge circuit (12) for rectifying alternating current power, a smoothing circuit (13) which has two capacitors (C1 and C2) serially connected to each other, and a PAM control section (15) for turning a switching element (S) on and off at a predetermined timing. The PAM control section (15) includes a phase difference detection section (15d) which detects a phase shift of a PAM waveform based on a change in a voltage difference between the two capacitors (C1 and C2), and a phase correction section (15e) which corrects the phase of the PAM waveform so that an input current has a sine waveform.

Claims

1. An electric power supply circuit comprising:

a rectifier circuit (12) which is connected to an alternating current power source (20) and which rectifies alternating current power;

a smoothing circuit (13) which has two capacitors (C1 and C2) serially connected to each other and which is connected to an output side of the rectifier circuit (12);

a switching element (S) which, when turned into an ON state, connects the alternating current power source (20) and a midpoint between the two capacitors (C1 and C2) and which causes a short circuit of an output power of the rectifier circuit (12); and

a PAM control section (15) which outputs a pulse signal for switching the switching element (S), at a predetermined timing based on a zero-cross point of an input voltage of the rectifier circuit (12), wherein

the PAM control section (15) includes;

a phase difference detection section (15d) which detects, based on an amount of charge in the two capacitors (C1 and C2), a shift between an output phase of the pulse signal and a phase of a pulse signal that makes an input current of the rectifier circuit (12) have a sine waveform; and

a phase correction section (15e) which corrects the output phase of the pulse signal so that the phase shift detected by the phase difference detection section (15d) is removed.

2. The electric power supply circuit of claim 1, wherein

the phase difference detection section (15d) is configured to detect the shift between the output phase of the pulse signal and the phase of the pulse signal that makes the input current of the rectifier circuit (12) have a sine waveform, based on a voltage difference between the two capacitors (C1 and C2).

3. The electric power supply circuit of claim 2, wherein

the phase difference detection section (15d) is configured to detect the shift between the output phase of the pulse signal and the phase of the pulse signal that makes the input current of the rectifier circuit (12) have a sine waveform, based on a change in the voltage difference between the two capacitors (C1 and C2), the change in the voltage difference between the two capacitors (C1 and C2) being obtained by comparing voltage differences during periods in which the switching element (S) is in an OFF state for more than a certain period of time in one cycle of the input voltage.

4. The electric power supply circuit of claim 1, wherein

the phase difference detection section (15d) is configured to detect the shift between the output phase of the pulse signal and the phase of the pulse signal that makes the input current of the rectifier circuit (12) have a sine waveform, based on a voltage change of one of the two capacitors (C1 and C2).

5. The electric power supply circuit of claim 1, wherein

the phase correction section (15e) is configured to correct the output phase of the pulse signal in stages according to the amount of charge in the two capacitors (C1 and C2).

6. The electric power supply circuit of claim 1, wherein

the PAM control section (15) further includes:

a zero-cross detection section (15a) which detects that the input voltage of the rectifier circuit (12) has increased to be equal to or higher than a predetermined value and is approaching the zero-cross point; and

a PAM waveform output section (15b) which outputs an ON pulse to the switching element (S) when the zero-cross detection section (15a) detects that the input voltage of the rectifier circuit (12) has increased to be equal to or higher than a predetermined value and is approaching the zero-cross point.

7. A PAM control method for an electric power supply circuit comprising:

a rectifier circuit (12) which is connected to an alternating current power source (20) and which rectifies alternating current power;

a smoothing circuit (13) which is connected to an output side of the rectifier circuit (12) and which has two capacitors (C1 and C2) serially connected to each other,

a switching element (S) which, when turned into an ON state, connects the alternating current power source (20) and a midpoint between the two capacitors (C1 and C2) and which causes a short circuit of an output power of the rectifier circuit (12); and

a PAM control section (15) which outputs a pulse signal for switching the switching element (S) at a predetermined timing based on a zero-cross point of an input voltage of the rectifier circuit (12), wherein

the PAM control section (15) detects a voltage difference between the two capacitors (C1 and C2), and corrects an output phase of the pulse signal in stages according to the voltage difference between the two capacitors (C1 and C2) so that the output phase of the pulse signal is a predetermined phase that makes an input current of the rectifier circuit (12) have a sine waveform.